1942: Botany

Plants Bottlenecked by the War.

In the year 1942, the first year 'after Pearl Harbor,' there have been, as a direct result of the war, drastic curtailments in supplies of many essential materials, some of which are dependent for their continued production on plant science in some of its branches, e.g., agriculture, forestry, horticulture; and for the development of new sources, on taxonomy, ecology, anatomy, genetics, etc.

Rubber.

The most important of these materials perhaps is rubber. At the present time about 9/10 of this country's supply of crude rubber, derived mainly from Hevea brasiliensis, a tree member of the spurge family or Euphorbiaceae, has been bottlenecked by the war. Hence there is an urgent need for substitutes, which our scientists, plant and otherwise, have been busily investigating. Guayule, Parthenium argentatum, a small shrub of the composite or sunflower family, is one of those substitutes which can be grown readily in the southwestern United States, where it is in fact native, and grows naturally also in northern Mexico. The President's rubber survey committee, headed by Bernard M. Baruch, has stated that guayule is the principal source of natural rubber that could not be lost to us short of conquest of American territory. Officials of the Forest Service (which has carried on the program of seed collecting and planting) stated recently that 'domestic production in California should amount to 600 tons this winter from mature shrubs previously reserved for seed production.' It is expected to step up sharply to 33,000 tons in the winter of 1944-45, and to 47,000 more tons the following year. Another possible source is the Russian dandelion, Taraxacum Kok-saghyz, also a member of the sunflower family, experimental plantings of which are being made. Synthetic rubbers, for some of which advantages over natural rubber are claimed, are also being manufactured and used by various large rubber concerns, which in some cases had already been working in these products for many years. It should be noted, further, that 2,500,000 plants of Hevea have recently been planted in Haiti where at least 100,000 acres are available for a nearby supply. Also, investigators in the Department of Agriculture are working on a process for the transformation of soybean meal into rubber.

Sugar.

Confronted with a sugar shortage, a larger acreage is being planted to sugar beets, and a new method of seed preparation has been developed for beet 'seed' (strictly a fruit containing several seeds). The production of sorghum for sweetening and of maple sugar is being stepped up. Honey is taking on added significance as a sugar substitute.

Cork.

Experiments in planting cork oak, Quercus suber, from which commercial cork is obtained, are planned by the U. S. Dept. of Agriculture, if acorns can be obtained from the Mediterranean countries. Normally this country imports about $10,000,000 worth of cork each year from Spain, Portugal, and North Africa. Texas, New Mexico, Arizona, and southern California have a climate similar to that of these countries, and the cork oak should grow well in these states.

Drug Plants.

Prof. W. J. Bonisteel, of Fordham University, states that four of the most important drug plants, namely digitalis, belladonna, stramonium and henbane could be raised in sufficient quantity in 1,000 acres to supply all United States needs. Some of the other drug plants that can be satisfactorily grown in this country or elsewhere in the hemisphere include castor oil beans, ginger, orris root, citronella, henna, ergot, and members of the anise-dill-fennel group.

Spray Materials.

As regards the shortage of spray materials for insecticides and fungicides, Neely Turner and James G. Horsfall at the Connecticut Agricultural Experiment Station at New Haven state that 'the means for saving spray materials are legion. Perhaps the most important of these are (1) to use them in troubles that can be controlled, (2) to treat only plants that are likely to be most in need, (3) to improve the efficiency of distribution over the plants, and (4) to give careful attention to the dosages.' These investigators recommend various chemicals which for certain purposes can replace copper, mercury and formaldehyde.

Researches in 1942.

The trend of former years, away from taxonomic and morphological studies of plants, has been maintained. The majority of researches continue to deal with the physiology of plants, i.e., how they behave, or respond, both normally and under special conditions of environment.

Physiological Studies.

Fritz Wendt of the California Institute of Technology, working mainly with tomatoes, finds that, for 'setting' their fruit, they need the alternating light and darkness of day and night, together with concomitant diurnal rise and fall of temperature. This phenomenon has been termed 'thermo-periodism.'

J. V. Overbeek, Marie E. Conklin, and A. F. Blakeslee of the California Institute of Technology at Pasadena and of the Department of Genetics of the Carnegie Institute of Washington, at Cold Spring Harbor, N. Y., have grown young embryos of Datura in vitro for a considerable period, using an agar medium containing dextrose, mineral salts, a mixture of physiologically active substances, plus coconut milk. In one case, after 10 days in the medium, the embryo had increased 8,000 times in volume. Viable seedlings were obtained by transferring these 'incubated' embryos, after one week, to a medium without coconut milk, since the latter was found to inhibit root growth. Roots then developed and viable seedlings resulted.

In the culture of barley embryos in vitro James Merry of Denison University found that with embryos less than 10 days old no cell division occurred. In embryos 12 days old or older, cells continued to divide as long as the plants were grown in the culture.

Nellie A. Brown of the U. S. Horticultural Station at Beltsville, Md., reports that brushing plant tumors with colchicine results in their death.

Methods of extracting auxin from wheat are described by G. S. Avery, Jr., J. Berger and B. Shalucha of Connecticut College; and its extraction from various plant tissues by Kenneth V. Thimann, Folke Skoog and Ava C. Byer of Harvard University.

Morphology and Taxonomy.

Carl S. Wilson of Dartmouth College brings out additional evidence in favor of the telome theory of the phylogenetic origin of floral organs, in particular of the stamen. Stated in simple language, the telome theory postulates that floral organs arose directly from the modification of stem structures, and were not metamorphosed leaf structures, the latter idea having been generally accepted until recently. Studies on the morphology of the Caryophyllaceae (Pink Family), made by Betty Flanders Thomson of the University of Vermont, confirm the view that this family is related to the Primulaceae (Primrose Family).

Robert T. Clausen of the Bailey Hortorium and Cornell University has presented a taxonomic study of part of the genus Sedum, a large genus of flowering plants in the Orpine Family, Crassulaceae.

Fungi.

Ray R. Hirt and Henry Hopp of the New York State College of Forestry at Syracuse, N. Y., find that in the fungus Fomes igniarius, the sporophores (the woody brackets that grow on trunks or branches of trees) normally form one layer of tubes each year.

David L. McVickar, working at Harvard University, reports that the fungus, Pilobolus, which commonly occurs on horse dung, exhibits a diurnally rhythmic asexual reproduction. Ripening of the spore-bearing organs, which normally occurs during the morning, can be made to occur at any hour of the day or night by suitable adjustment of alternating 12 hour periods of light or darkness.

M. H. Langford and G. W. Keitt of the Wisconsin Agricultural Experiment Station at Madison, in a study of Venturia pirina, the causal agent of pear scab, find that although the fungus is hermaphroditic, it is heterothallic in the sense that the thalli are self incompatible and 'comprise at least 2 groups that are intra-group incompatible and inter-group compatible.'

Diseases.

Clayton O. Smith of the California Citrus Experiment Station at Riverside, California has artificially induced crown gall on various species of conifers, by inoculating them with Phytomonas tumefaciens.

G. H. Parris of the Hawaii Agricultural Experiment Station, reports a disease of papaya, Carica papaya, fruits induced by the fungus, Phytophthora parasitica.

At the Connecticut Agricultural Experiment Station, work is now going forward on a method of preventing, or at least retarding, the growth of the causal fungus in the Dutch elm disease. This is done by the injection of chemicals which either counteract the toxic effects of the fungus, or kill the protoplasm of the fungus without producing deleterious effects on the tree itself. For this purpose, benzoic acid, hydroquinone, and 8-hydroxyquinoline benzoate have so far given good results. However, the work is still in the preliminary stage.

1941: Botany

In spite of the war, researches in plant science continued much as usual, at least in the United States; but this was unfortunately not true of the old world countries, where much of the energies and resources were perforce directed elsewhere. In this country the general interest in the effect of chemical substances on plant growth and development continued and a large number of papers along this line appeared. It is, however, impossible, for lack of space, even to name all of the brilliant papers on this and other subjects.

Morphology.

Among notable papers on morphology and anatomy of plants are the first in a series of studies on the phloem of monocotyledons, by Vernon I. Cheadle and Natalie B. Whitford of Rhode Island State College at Kingston, R. I.; on megasporogenesis and embryo-sac development in Calochortus, one of the Liliaceae, by Marion S. Cave, of the University of California, at Berkeley, Calif., on the morphology of Regnellidium diphyllum, by Noe Higinbotham of Columbia University, New York City; on the development of rays in the dicots, by Elso S. Barghoorn, Jr., of Harvard University; on some histogenic features of the shoots of Cryptomeria japonica, by G. L. Cross of the University of Oklahoma, at Norman, Okla.; on fertilization in Vallisneria, by R. B. Wylie of the University of Iowa at Iowa City.

Deficiency in Mineral Elements.

A considerable amount of matter has been published relating to the effect of a deficiency of mineral elements, including the so-called 'trace' or minor or 'micro-elements,' such as boron or zinc, on vegetable crops. In some publications, colored photographs of leaves of various crop plants are presented, showing definite color changes or mottlings which are called 'hunger signs.' These are extreme cases, but they are supported by experimental work. The symptoms under field conditions, on account of the complex nature of the environment, are probably rarely as clearly cut as those depicted.

Hormones.

Vitamin B₁.

One of the sensations of the year has been the bursting of the vitamin B₁ bubble; which, by-the-way, had grown to a large size. As to the nature of this plant hormone, Dr. G. S. Avery, of Connecticut College, a recognized authority on plant hormones, says that it is 'normally produced in the green tissues of the plant, and is transported to the roots. Root growth, in many species at least, cannot go on without it. If roots are cut off from the parent plant and then grown in a culture medium, vitamin B₁, or thiamin, has to be added to the nutrient medium.' Dr. Alvin J. Cox, Chief of the Bureau of Chemistry, Calif. Dept. of Agriculture, says: 'A small amount of vitamin B₁ is believed continually required in the life processes of both animals and plants.'

The beginning of the vitamin B₁ craze can be traced to an article in one of the magazines on gardening which appeared in October 1939, with the headline as follows:

'News of an exciting discovery ... of five-inch rose buds, daffodils bigger than a salad plate, snapdragons six feet tall, roses transplanted while flowering ... the story of a miracle-working powder and how to use it indoor and outdoor gardening this fall.'

This craze has lasted more than a year, during which time many enterprising floriculturists and seedsmen have fattened their pocketbooks by reason of the alleged miraculous powers attributed to vitamin B₁; but at length the credulous public is being quietly disillusioned by sober scientists. Dr. P. W. Zimmerman of Boyce Thompson Institute at Yonkers, N. Y., writes in the American Rose Annual for 1941 as follows:

'The preponderance of evidence from scientists is opposed to the use of vitamin B₁ for practical purposes. My own convictions, based on our experience at the Boyce Thompson Institute and the published results of other scientific laboratories, are that vitamin B₁ has been badly exploited, and that it has no value as recommended for horticultural practice.'

And a bulletin issued in June 1940 by the State of California Department of Agriculture (Vol. 29, No. 2, pp. 106-109) refuted the claims made for vitamin B₁ and showed how the sale of it and the claims made for it in California represented a misdemeanor. The bulletin states:

'As a whole it is believed not proved that the artificial addition of vitamin B₁ will produce a beneficial effect on plants, but there are exceptions ... The question of adding vitamin B₁ to commercial fertilizers needs a great deal of research before it is undertaken.'

Dr. Zimmerman, in a letter to Dr. J. H. McFarland, printed in the American Rose Magazine for November-December 1941, says ... 'The scientists in general have completely discredited vitamin B₁ for practical purposes.' The conclusion of the whole matter is that vitamin B₁ is not a miracle worker, but it has been demonstrated that in many species of plants (not in all) roots cannot grow unless it is present in minute amounts. A small amount, also, seems to be necessary for normal metabolism.

Sulfanilamide.

Among the papers presented at the fiftieth anniversary celebration of the University of Chicago was one by Prof. John M. Beal which stated that sulfanilamide produces effects similar to those brought about by colchicine, stopping the process of mitosis or cell division midway, thus causing the formation of extra large cells which double or quadruple the number of chromosomes.

Growth hormones in general have been recently used for producing seedless fruits from unpollinated flowers, e.g., seedless tomatoes and holly berries. Spraying orchard trees with the hormones has had the effect of inducing apple and other trees to hang on to their fruit instead of dropping prematurely, and of hastening the ripening of oranges.

New Sweet Corn.

A wilt-resistant hybrid yellow sweet corn has been developed by E. S. Haber, research horticulturist at Iowa State College. This new hybrid has consistently outyielded Golden Bantam from 60 to 80 per cent, often actually doubling the weight of ears per acre. The new hybrid is resistant to bacterial wilt and to smut, can be grown from coast to coast in the northern United States, and has been grown successfully in Texas, Louisiana and some of the other southern states.

Diseases of Trees.

A new disease of cherry trees called 'vein clearing' causing a loss of green color along the leaf veins and a general mottling of the leaf surfaces, has been described by S. M. Zeller and A. W. Evans of the Oregon Agricultural Experiment Station at Corvallis. Prunes as well as cherries, both important commercial crops in the Pacific Northwest, are attacked. The disease, caused by a virus, transmissible by grafting with diseased stock, has been found also in ornamental flowering cherries, on Italian prunes, and on several species of wild cherry.

Winter Injury.

In the region about New York City, including northern New Jersey and southwestern Connecticut unusual weather conditions resulted in the killing back of thousands of rhododendrons, both native and hybrid forms. A fairly mild period during the early part of March was followed by severe winds with low temperature. This caused the leaves to roll up tightly, dry out; and in more exposed places a large part of the plant or even the whole plant was killed. The rather dry condition of the soil resulting from low rainfall in 1940 was doubtless also a contributing cause of the damage. Mountain laurel (transplanted) was affected to some extent, and later, in April, many of the members of the pine family were affected. The extremely dry weather during 1941, at least in the eastern states, augurs ill for trees and shrubs, for they will enter winter with a dry soil and subsoil and will, therefore, be more susceptible to injuries such as the above. On the other hand the normally drier areas of the midwest have, in 1941, received a marked excess of precipitation.

Dutch Elm Disease.

Several times of late years it has been reported that the spores of the fungus responsible for the Dutch elm disease can be transported lengthwise in the trunk in the vessels or pores of the wood. This is an unusual method, indeed, for dissemination of disease, but it is possible and understandable here because the fungus in question can form spores in the interior of the wood in the vessels themselves. Now Dr. W. M. Banfield of the Division of Forest Pathology, U. S. D. A., stationed at Morristown, N. J., at one of the laboratories for the study of the Dutch elm disease, has removed all doubt about the matter. By field experiments, using the American and slippery elms, he has shown conclusively that the spores are readily transported by the sap stream in the vessels of the wood. As one would suspect, a priori, this movement is rapid during the spring season, averaging more than 44 feet in trees 50 feet in height in from 20 minutes to 48 hours. In the summer the movement is less rapid and extensive, and in the 'non-leafy season' the spores 'could not be recovered at more than 24 inches above injection points.' This method of transport was also found to be true of other wilt producing fungi, namely, Verticillium dahliae and Dothiorella (Cephalosporium) ulmi.

As regards the spread of the disease in the United States there has been but little enlargement of the infected area of 1940. The first occurrence in Massachusetts was reported in 1941 in the town of Alford: other localities where the disease has been found, such as Old Lyme, Conn., Cleveland, and Cincinnati and a few others have had no recurrence of the trouble. This is in marked contrast to the rapidity with which the chestnut blight swept the country.

1940: Botany

A review of the 1940 researches in plant life must take into account the disastrous influences of the widespread European war, and of the wars in the Far-East. In Europe and in Japan, as is to be expected, research was curtailed and correspondence between scientists in these countries and America was difficult or impossible. Subscriptions to our American botanical magazines in many cases were terminated, resulting in a diminution of funds available for publications here. Chronica Botanica, formerly published in Holland, has been transferred to the New World, and is now published in Waltham, Mass. Published weekly, it 'gathers all scientific, professional, and personal news and comments which may help plant scientists (now over 80,000 in about 4,000 institutions) with their current work and new projects.'

The herbaria of the department of botany of the British Museum, together with original drawings, manuscripts and valuable books, have been moved and stored in such a way that they will be as safe as possible, but still may be consulted if necessary.

The herbarium of the Musée d'Histoire Naturelle, Paris, which after the outbreak of the war was divided among three castles near Paris for safe keeping, is in good condition and has been returned to the Musée.

Here in the United States plant research in the hundreds of institutions — state experiment stations, college and university departments, botanical gardens, and private foundations has gone forward as usual, resulting in a host of scientific papers of outstanding merit, of which there is space here to outline only a few.

As in recent years, a large number of researches deal with problems in plant physiology and particularly with the effect of chemical substances, plant extracts, etc., on plant life and development. Many notable papers on morphology have appeared, such as that by A. S. Foster of the University of California at Berkeley, on the shoot apex of Cycas revoluta; by J. T. Buchholz of the University of Illinois, on the embryogeny of Torreya; and by Fred T. Wolf of Vanderbilt University, Nashville, Tenn., on the development of the female gametophyte in Yucca aloifolia. Valuable taxonomic papers have appeared such as: the Oscillatoriaceae of Virginia by J. C. Strickland of the Miller School of Biology, University of Virginia at Charlottesville, Va.; plants from northern South America by A. C. Smith, of the New York Botanical Garden, to name only two of many notable papers in this field. Albert H. Tillson of the Division of Plant Exploration and Instruction, Bureau of Plant Industry, U. S. Dept. of Agriculture, finds in a study of the subfamily Kalanchoideae of the Crassulaceae that on the basis of their vascular anatomy in the floral region, Bryophyllum and Kitchingia are valid genera, but that Kalanchoe Fedtschenkoi, K. Gastonis-Bonnieri, and K. Waldheimi are really species of Bryophyllum. (See also HORTICULTURE.)

Photoperiodism.

The striking researches of H. A. Allard and W. W. Garner of the Bureau of Plant Industry, on the response of plants to the relative length of daylight were published in 1920 and 1923. Before the work of those investigators the fact that the relative length of day is really a dominant factor in plant reproduction seems not to have been suspected. They found that certain plants (short day plants) flowered under the influence of short daylight periods, thus in the early spring or in the fall; while other species (long day plants) bloomed under the influence of long days, i.e., during the summer. They found, too, that short day plants exposed to longer illumination each day by artificial means would flower tardily or not at all. The same was generally true of long day plants, exposed to shorter light periods than those to which they were accustomed. In a publication of the Bureau of Plant Industry this year they give the results of further experiments in this field, extended to both wild and cultivated plants. For example, most of the asters, which bloom naturally in the fall, are short day plants. However, if their period of illumination is artificially shortened earlier in the season, they may be brought into flower in June or early July. On the other hand, long day plants, such as Gladiolus gandavensis and Iris florentina, may have their flowering inhibited by shortening their exposure to light to 12 hours a day. Further, some plants, such as the wild Polygonum pennsylvanicum, are apparently indifferent to the length of daylight in so far as its effect on their flowering period is concerned. Practical applications of this remarkable discovery are, e.g., the practice of chrysanthemum growers in forcing their crops into earlier flowering by the use of black cloth to shorten the daylight period. Electric light has been used to supplement short days for the China aster (a long day plant) thus forcing the plants into earlier flowering.

Fungi.

W. J. Robbins, working at the New York Botanical Garden and at Columbia University, finds that extracts of the mycelium of Phycomyces favorably affect the germination of its spores, and at least the early growth of its mycelium, cultivated in a medium of minerals, sugar, asparagine, and thiamin. Extracts of mycelia of various ages increase in effectiveness with the age of the mycelium, and then decrease, showing some correlation with the rate of growth of the mycelium from which the extracts were prepared.

G. M. Watkins and Matilde Otero Watkins of the Texas Agricultural Experiment Station in a study of the pathogenic action of Phymatotrichum omnivorum, the fungus responsible for a root rot of the cotton plant, conclude that exudates from the mycelium of this fungus contain thermolabile substances, probably enzymes, which are largely responsible for the destruction of host cell walls during infection. This is quite in line with the action of many so-called parasitic fungi, which kill the cell before they invade it.

An important contribution to our knowledge of parasitism in fungi was the discovery, by G. M. Reed in 1924, of physiologic races of oat smuts. Working at the Brooklyn Botanic Garden, Reed found that certain smuts, although apparently identical in outward appearance, manifested a differential behavior when applied to certain varieties of oats, that is, a smut (Ustilago levis) from Wales when applied to Avena brevis (a variety of oats) infected it, but gave practically negative results on Avena sativa. On the other hand, what was apparently (morphologically) the same smut, collected at Columbia, Missouri, infected Avena brevis only slightly, but attacked several varieties of Avena sativa. In other words, two fungi, although apparently of the same species, may not possess the same internal propensities — somewhat as in the case of human twins, apparently identical, but one with a good and the other with a mean disposition. Now Reed comes forward with a new paper in which he announces (in all) 'twenty-nine physiologic races of Ustilago avenae and 14 of U. levis differentiated on the basis of their behavior on definite strains and varieties of nine species of oats.'

Diseases of Trees.

The Ceratostomella disease of the plane tree has recently been reported by Paul V. Mook, of the division of Forest Pathology, U. S. Department of Agriculture, as affecting considerable numbers of London planes (Platanus acerifolia) near Wilmington, Delaware, where a number of trees are already dead. Also, at Knoxville, Tenn., a large American plane or sycamore (P. occidentalis), and at Middlesboro, Kentucky, two American planes were found in advanced stages of the disease. Ceratostomella, the causal fungus, produces a 'bluish black, moist-appearing wood discoloration,' which is the principal internal symptom. Authentic reports of this apparently new disease have come previously from Pennsylvania, Maryland, New Jersey, and the District of Columbia. The London plane is a tree admirably adapted to succeed in large cities on account of its tolerance of dust, smoke and gases, and drought. But, in view of these reports, city authorities should await further developments before making extensive plantations of this species.

As to the Dutch Elm disease, a slight increase of the infection area has been reported, but nothing at all comparable to the rapid spread of the chestnut bark disease, which has now killed off practically all our large chestnut timber trees.

1939: Botany

Investigations in plant science during 1939 succeeded in many fields in pushing still farther back the film that divides the known from the unknown. Biological Abstracts, the journal which contains the gist of biological papers published from month to month throughout the scientific world, and which was threatened with collapse in 1937, has now been placed on an even keel. It is reported that in 1939 this journal published abstracts of 18,108 papers, as against 16,323 in 1938. In October 1938, 575 scientific journals were covered, but in October 1939, that number was raised to 1,113.

It is of course impossible in limited space to review in detail this vast amount of material. It is possible to select only certain pieces of research which seem valuable either from the point of view of pure science or important from an economic standpoint; and meanwhile to indicate the general trend of thought in plant science. Much that is doubtless of equal importance must be omitted.

Hydroponics.

The rage for growing plants by the water-culture method, i.e., by adding the requisite mineral elements in solution to the water in which the roots of a plant are immersed, continues unabated. It is an old idea — not really new knowledge — but because of much advertising it has caught the popular fancy. School children are trying it; enthusiastic, budding scientists have chosen it for a hobby. In so far as it propagates a knowledge of 'how plants grow' it is good. The only way in which it can possibly claim an advance in our scientific knowledge is its application on a commercial scale to growing large crops. But on this point, D. I. Arnon and D. R. Hoagland, of the College of Agriculture, University of California, declare:

'It must be clearly recognized that the application of the water-culture method for crop production will be limited primarily by economic considerations. . . . It seems highly improbable, in view of the present cost of a commercial water-culture installation and its operation, that crops grown by this method could compete with cheap field-grown crops. In greenhouses specializing in high-priced, out-of-season crops the method appears to have commercial possibilities. The expense of growing greenhouse crops in soil, including cost of equipment for sterilizing soils, may frequently stand comparison with the cost of growing crops by the water-culture method. . . . The suggestion that important amounts of food could be produced economically in small-scale installations for home use has no sound basis, because of high costs of the installations and technical requirements for the successful use of the method.'

Hormones.

Hormones, i.e., substances which bring about specific physiological reactions, are generally held to include the auxins and are divided by Huxley (1935) into 2 groups: A, regional activators and B, distance activators. J. R. Raper of Harvard University, in a study of the sexual relationships of Achlya, one of the water molds, concludes that several hormones operate here in the formation of sexual organs. James Bonner and Philip S. Devirian, of the William G. Kerekhoff Laboratories of the Biological Sciences, California Institute of Technology at Pasadena, Calif., find that isolated pea roots can be cultivated indefinitely in nutrient media containing vitamin B₁ and nicotinic acid, in addition to mineral salts and 4 per cent sucrose. But substances requisite for growth vary with different species. In flax roots, for example, vitamin B₁ is the only accessory growth factor required.

W. J. Robbins, of the New York Botanical Garden, has shown (1938) that some fungi are able to synthesize a growth substance (vitamin B₁) known as thiamin, provided they are supplied with the necessary chemical elements. He now finds that other fungi, which are heterotrophic, i.e., unable to synthesize this growth substance, will thrive when in the proximity of fungi autotrophic for thiamin, and suggests 'possible nutritional relationships between symbionts and between parasite and host, other than those involving carbohydrate and nitrogen compounds hitherto commonly assumed.'

Cellulose.

Cellulose (C₆H₁₀O₅)n, an organic substance peculiar to plant life, has become indispensable to our civilization. Cotton is almost pure cellulose, and, in a slightly altered chemical state, cellulose forms the basis of wood. Closely related to starch (C₆H₁₀O₅)n, and sugar, it forms the chief structure of the membranous cell-walls of plants, and is permeable to watery solutions. Just how and where it forms have always been a mystery. Now Dr. Wanda K. Farr of the Boyce Thompson Institute at Yonkers, N. Y., finds that it is formed within the plastids (disc-like bodies) in the plant cell. At least this is true of the alga Halicystis, and also of the cotton plant. It originates as small, ringlike structures inside the plastid, which grow until the membrane of the plastid breaks down. The rings are then released and subsequently break up into cellulose particles. The particles are of the same size, since the rings are of the same thickness, throughout. It appears reasonable to assume that the cellulose is formed in the plastid directly from the photosynthetic sugar.

As to the way the cell wall is built up, I. W. Bailey, of Harvard University, suggests that the cellulose matrix 'is composed, in the submicroscopic field, of aggregations of chain molecules that are held together by overlapping chain molecules. In the microscopically visible field, it is constituted of coalesced microfibrils. In both fields of magnitude, the continuous cellulosic system is perforated by a continuous system of interconnecting capillary spaces.'

Tissue-culture Experiments.

Philip R. White, of the Rockefeller Institute for Medical Research at Princeton, N. J., has carried small cones of tissue taken from near the stem tip of a hybrid Nicotiana in a living and growing condition in nutrient agar cultures for 40 weeks without evident differentiation, and apparently with unlimited capacity for growth. This was in a semi-solid (agar) medium. However, after transfer to a liquid medium, differentiation began to take place, growing points and even small leaves forming, showing that the 'cell groups were nearly if not completely totipotent.' He suggests that the difference in oxygen conditions may produce these different results.

Morphology.

J. T. Buchholz, of the University of Illinois, presents a careful study of the morphology and embryology of Sequoia gigantea, the 'Big Tree.' He finds that in its development the female gametophyte follows the usual program observed in other conifers, in its embryogeny resembling most closely that of Sciadopitys. In a later paper, in which he presents a similar study of Sequoia sempervirens, the Redwood, he finds sufficient differences between these two species (as they are now classed) to warrant their being placed in separate genera.

From ontogenetic studies of flower buds, A. Gundersen, of the Brooklyn Botanic Garden, finds that parietal placentation is the earlier condition; for those flowers with axile placentation usually have, in the beginning, parietal placentation, i.e., in the bud stages. He believes, therefore, that in a natural classification, groups such as the Opuntiales, Parietales and Papaverales should be placed together early in the system.

Plant Diseases.

P. R. Miller, of the Division of Mycology and Disease Survey of the Bureau of Plant Industry, U. S. Department of Agriculture, finds that in the Apple-rust—Cedar-apple disease, in which the casual fungus Gymnosporangium juniperi-virginianae lives alternately on apple and species of Juniperus, the aeciospores from the fungus on the apple infect Juniperus at two fairly distinct periods, first toward the end of the summer, and second (and more commonly) in early spring. Fungicides applied to Juniperus during the winter should therefore be effective in the control of the disease. O. C. Anderson, in a study of the blister-rust-resistant Viking red currant, finds that the resistance to infection is 'physiological rather than physical'; i.e., there seems to be some protoplasmic incompatibility which prevents the growth of the fungus in the host cells.

Dutch Elm Disease.

From Jan. 1 to Sept. 9, it was found that 10,246 trees were affected with the Dutch Elm Disease — most of them (8,438) in New Jersey. Several new counties in New York State and New Jersey have been added to its range. Apparently the disease is spreading, though very slowly, in spite of the determined efforts of the U.S.D.A. to eradicate it. See also BIOLOGY; HORTICULTURE.

Paleobotany.

See GEOLOGY.

1938: Botany

Hydroponics.

Dr. W. F. Gericke, of the University of California is responsible for the development of the new science of Hydroponics. This means, briefly, growing vegetables and flowers in tanks to which nutrient salts have been added. It has been known for nearly a century that such a practice is feasible. What Dr. Gericke has done is to show that it may have a commercial application.

'Four commercial growers are using the Gericke methods, under his supervision. One of these, at Montebello, Calif., has grown premium tomatoes which sold for $262 per ton at the rate of 100 tons per acre of water. Gericke does not ask for fees from these companies. 'All I want,' he says, 'is for them to set aside sufficient funds for me to carry on experiments.'

'He objects to the fact that a dozen or more small chemical companies have sprouted up to sell nutrient salts to amateurs or professionals experimenting with hydroponics. These have names like Chemi-grow, Chemi-Crop Company, Shur-Gro Fertilizer Corporation. They are legally within their rights, since hydroponics cannot be patented. The only patent which Dr. Gericke holds is for a container to diffuse the chemicals through the solution. But he argues, against the companies, that no formula works well for all plants, all climates, all conditions; and that, even if they made a great variety of formulae, there are other factors, such as temperature and acid-alkali balance, which must be thoroughly studied for successful hydroponics. Also, in his kindly if eccentric way, he accuses them of victimizing 'poor people' by selling chemicals worth a few cents at fancy prices ranging from one to three dollars.'

The chief objection, so far advanced, to these methods, is that they are expensive and difficult to control on a large scale. But that the new science has made a great stir there can be no question. Even a magazine called Hydroponics, The Magazine of Gardening without Soil was inaugurated in the spring of 1938.

As having a bearing on this subject, we should note the work of D. I. Arnon, of the University of California. Growing lettuce and asparagus plants in ordinary culture solutions, he found that a marked increase in growth was obtained by the joint addition of boron, manganese, zinc and copper, confirming results already obtained by others; also, that a further significant increase resulted from the addition of a group of seven elements — molybdenum, vanadium, titanium, tungsten, chromium, nickel, and cobalt — a fact suggesting that one or more of these last seven elements is important in the nutrition of higher plants.

Dr. E. M. Hildebrand, of Cornell University, in an admirable paper published in the Botanical Review, has brought together the various techniques for the isolation of microorganisms. To those who desire to obtain a pure culture of any particular microorganism, this paper is extremely helpful.

Colchicine.

The exact way in which colchicine affects plant tissue seems still to be more or less in doubt. According to Ruth Walker, of the Extension Division of the University of Wisconsin, colchicine 'does not seem to have any visible effect on the chromatic material.' It works rather upon the cytoplasm and the spindle in mitosis, and as a result the formation of the spindle and the new cell wall is suppressed. As a result of the first meiotic division we find, therefore, an apparently diploid nucleus (instead of a haploid), and by suppression of the walls of the next division we may have a tetraploid nucleus. This means that pollen grains formed under those conditions may be provided with double or quadruple their normal number of chromosomes.

The Fungi.

Working on the effect of light on the fruiting of myxomycetes, Dr. William S. Gray, of the University of Pennsylvania, found that, of the species studied, yellow pigmented types require light to complete their life cycles, while non-pigmented types and Didymium xanthopus fruit equally well in light or darkness.

Dr. B. O. Dodge and Bernice Seaver, of the New York Botanical Garden, in further breeding work with the fungus Neurospora tetrasperma, find that the two types of lethal factors they had already described — one causing induration and the other, deliquescence of the ascus — 'segregate independently in regular order and react without serious interference, each producing abortion of the ascus in its own way.'

Physiological Researches.

Dr. Raymond H. Wallace, of Connecticut State College, at Storrs, Conn., and Harold H. Clum, of Hunter College, New York City, in a study of leaf temperatures, conclude that transpiration (i.e., the giving off of water vapor from the leaf) is necessary at times to prevent leaves or parts of leaves from being injured by extreme heat.

It is generally known that in the chestnut blight the foliage above the attacked portion of the shoot withers and dies, and it has been assumed that in some way the supply of sap was cut off through the activity of the fungus. Now Dr. W. C. Bramble, of the Pennsylvania State College, shows that such stoppage is due to the abnormal formation of tyloses (cellular growths into the water-carrying pores) in the sapwood in the region of the fungous lesion. These tyloses, apparently the result of some kind of stimulation by the fungus, protrude into the conducting elements and thus block the passage of the sap through the wood.

Plant Hormones.

The study of the effect of growth hormones on plant tissues has continued, with some slight decrease in amount of published material. To date, seven monographs on the subject have appeared. The book 'Growth Hormones in Plants' by Drs. G. S. Avery and P. R. Burkholder, of the Connecticut College at New London, has already been reprinted; a second edition is being prepared.

Plant Diseases.

Professor Ray B. Hirt, of the New York State College of Forestry at Syracuse University, reports that infection of the needles of the White Pine in the White Pine Blister Rust, may take place through the stomata, but suggests that direct penetration of the epidermal cells is probably the commoner method of infection.

A leaf blight of Iris caused by Bacterium tardicrescens is reported by Lucia McCulloch, of the U. S. Horticultural Station at Beltsville, Md. Working at the same station, Nellie A. Brown finds that the unsightly tumors or excrescences sometimes seen on oak or hickory trees are caused by a species of fungus (Phomopsis sp.) and not by Bacterium tumefaciens as has long been supposed.

Marion E. Fowler, of the Division of Forest Pathology of the U. S. Department of Agriculture, reports that the twig blight sometimes occurring in Asiatic chestnuts, particularly in those growing on poor sites, is caused by several species of fungi.

Systematic Studies.

In the short space allotted to us it is impossible even to mention by name all the excellent work of the past year dealing with the descriptions of new plant species and of plants of particular regions. We add: Studies of American Melastomes by Dr. H. A. Gleason, of the New York Botanical Garden; of Onagraceae by Professor Philip A. Munz, of Pomona College at Claremont, Calif.; on the fern group in the Galapagos and Cocos Islands, by Dr. H. K. Svenson, of the Brooklyn Botanic Garden; on Mississippi fungi by Dr. L. O. Overholts, of the Pennsylvania State College; on Zygnemataceae (a family of the green algae) by Professor Edgar Nelson Transeau, of Ohio State University at Columbus, Ohio; but there are many other botanists that have made distinct contributions to our knowledge of plant species.

Shelter Belt.

Regarding the trees planted by the U. S. Forest Service to form a shelter belt in the Midwestern States, the Forestry News Digest reports: 'Despite unusually severe drought conditions for 1935, 1936, and 1937, the trees . . . have done well, and in many areas the owners report that they are already receiving beneficial effects. On 13,556 farms more than 83,000,000 trees have been planted, proving that shelter belts can be successfully established in areas where tree growth is scarce, and crop rotation a serious need.'