Showing papers in "American Journal of Botany in 1943"

The tube method of measuring the growth rate of neurospora

Abstract: IN CONNECTION with investigations on the biochemical genetics of the ascomycete Neurospora, a technique has been developed for studying growth by measuring the progression of mycelial frontiers within horizontal glass tubes half filled with suitable solid culture media. This method is the equivalent of measuring the increase in radius of a circular colony, a method used by many workers in studying growth of fungi, bacteria, and tissue cultures. The tube method is particularly useful in studying growth rates of rapidly growing organisms such as Neurospora for which petri plate cultures of unwieldy dimensions would be required. Horizontal glass tubes for limiting mycelia to growth in one direction were used by Fawcett (1925) in determining growth rates of Pythiacystis citrophthora and Diplodia natalensis. It has been pointed out how "pyridoxinless" and "aminobenzoicless" mutant strains respond in such growth tubes to varying amounts of the vitamins pyridoxin and p-aminobenzoic acid, which these strains are unable to synthesize (Beadle and Tatum, 1941).While it is clear that this method is not universally applicable in bioassay procedures and not entirely free of disadvantages, it is nevertheless a method by which, under certain conditions, growth responses can be measured with precision. Accordingly, it is important to know in some detail the effects of various factors such as hydrogen ion concentration, temperature, etc., on this particular type of growth response. It is the primary purpose of this paper to supply such information. In planning the experiments reported, the use of the method for bioassays has been kept in mind, and attention has been directed particularly to such factors as might be expected to affect the method in this application. A "growth tube" assay of yeast extract for p-aminobenzoic acid has been made to indicate in principle how mutant strains might be used in bioassay work. THE ORGANISM AND ITS NUTRITIONAL REQUIREMENTS.-Under the name Monilia sitophila the imperfect stage of Neurospora has long been known as a mold infesting laboratories and bakeries. Several species are recognized (Shear and Dodge, 1927). N. sitophila and N. crassa are heterothallic, producing sexual spores only if the two mating types are present, while N. tetrasperma is heterocaryotic and facultatively heterothallic. These three species have been used in genetic studies following the demonstration by Shear and Dodge (1927) that their life cycles are particularly well adapted to such studies. One important advantage of Neurospora shared by 1 Received for publication July 17, 1943. Work supported by grants from the Rockefeller Foundation and from the Penrose Fund of the American Philosophical Society. 2 National Research Council Fellow, now at Columbia University, Department of Zoology. other fungi and many other organisms is that strains are readily propagated asexually and consequently can be maintained genetically constant as long as contaminations or mutations do not occur. Of the three species, crassa has been most extensively studied genetically, particularly by Lindegren (see review, 1942). The species sitophila, crassa and tetrasperma are able to grow on synthetic media containing inorganic salts, an inorganic nitrogen source, a suitable source of organic carbon, and the vitamin biotin (Butler, Robbins and Dodge, 1941, Beadle and Tatum, 1941). With the exception of biotin, all vitamins, amino acids, and other factors required are synthesized by the organism. Because Neurospora can be grown on a chemically defined medium, it has been possible to establish and detect mutant strains unable to synthesize particular vitamins, amino acids, and other substances. Such mutants, of which three have been described, are obtained as a result of X-ray or ultraviolet treatment. They are detected in a manner described elsewhere (Beadle and Tatum, 1941). With few exceptions, each of the mutant strains so far analyzed requires that only one specific substance be added to the so-called minimal medium. After obtaining the "pyridoxinless" and "thiazoleless" mutants in N. sitophila, a change to N. crassa was made because of its higher sexual fertility and because more is known about its genetics. The studies included in the present report, accordingly, are to a large extent confined to wild-type strains of N. crassa. In earlier experiments a single ascospore strain obtained from Dr. C. C. Lindegren was used. This strain is of mating type A (+ in the terminology of Lindegren). It is designated as "regular" and was used unless otherwise indicated. In later experiments a recently isolated single ascospore strain derived from "regular" was used and designated Number 1. This strain, also mating type A, has the same or nearly the same inherent growth rate as the "regular" one. Strain R977 grows somewhat faster and is of mating type a (-). Other strains are described in connection with the particular experiments in which they were used. Occasional reference to N. sitophila is made. In both form and rate of growth, the two species are so similar, however, that it is almost certain that the conclusions resulting from the strains on crassa will apply equally to sitophila. THE TUBE TECHNIQUE IN GENERAL.-The growth tubes adopted as a standard in the work reported here are made of 40 cm. lengths of pyrex glass tubing with an internal bore of about 13 mm. Terminal segments 5 cm. in length are bent up at an angle of 450, and the openings are fire polished and flared slightly (fig. 1). Such tubes can be held upright on

Chromosome number and phylogenetic relationships in the euphorb aceae

Abstract: THE EUPHORBIACEAE were first adequately delimited as a natural group of plants by A. L. de Jussieu in 1789. Since this time many contributions have been made to the classification, phylogeny, morphology and anatomy of the group. Though the family has been known for many years, considerable differences of opinion still exist as to the number of genera and species involved. Estimates of the number of species in the family vary from 3000 to 8000. The family is closely related to the Geraniales by structure of the gynoecium, although widely separated from other families in the order by the amount of reduction in most of its flowers (Willis, 1925). Small (1933) combines the Euphorbiaceae and the Callitrichaceae into a separate order-the Euphorbiales. This is placed between the Polygalales and the Sapindales, with the Geraniales immediately preceding this group. Pax and Hoffmann (1931) placed the Euphorbiaceae and the Daphniphyllaceae in the sub-order Tricoccae of the Geraniales. The family is characterized as follows: Flowers hypogynous, actinomorphic, mostly unisexual; perianth rarely double, usually simple or wanting; androecium 1oo; ovary of 3 carpels, trilocular, with 1 or 2 suspended ovules in each cell; micropyle directed upwards and outwards, and covered with a fleshy outgrowth (caruncle). Fruit almost invariably a schizocarp-capsule, splitting into carpels, often elastically. A few of the maj or taxonomic treatmen-ts of the Euphorbiaceae have been those of Baillon (1858), Bentham and Hooker (1883), Croizat (1936-42), Engler and Gilg (1924), Jablonsky (1915), Lanjouw (1931), Mueller (1866), Pax (1890, 191024), and Pax and Hoffmann (1919-31,). Many other taxonomic publications on small groups have added much knowledge as to the size, geographic distribution, economic uses, and relationships of the family and have made many changes in the fundamental lines of classification as outlined by Pax (1890) and Pax and Hoffmann (1931). The Euphorbiaceae are recognized as one of the larger families of the dicotyledons. They are a relatively natural group, although showing many lines of evolution. The impression exists among many plantsmen that the Euphorbiaceae have a general preference for semi-desert or desert regions, but a survey of the geographic distribution of the family proves this to be erroneous. Its members live in 1 Received for publication December 8, 1942. Appreciation is extended to the various Botanic Gardens and to numerous individuals who were so cooperative in furnishing seeds, cuttings and plants used in the course of this investigation, especially to Dr. Karl Sax, Biological Laboratories, Harvard University, for facilities which he so kindly provided and Dr. Leon Croizat, Arnold Arboretum, Jamaica Plain, Massachusetts, for the generous collection of Euphorbiaceous species and his invaluable aid in the identification of much of the material. varied habitats, in many different areas of the tropical and temperate world, and exhibit considerable diversity in growth types. Because of this great diversity of form and habitat, the family is of special interest. The Euphorbiaceae are of further interest due to the great diversity of chromosome numbers and chromosome sizes both between and within socalled natural groups. Certain tribes, or other taxonomic groups, appear cytologically to be natural groups in that one basic chromosome number is found in each, while in another group nearly all the basic numbers present in the family are found, suggesting that the unit is merely descriptive and artificial and not phyletic. The study reported here is concerned primarily with chromosome number and gross morphology. It is hoped that this study may prove to be of value in future taxonomic studies. MATERIALS AND METHODS.-The materials used were grown from seed, from cuttings, or were obtained from various sources as small plants. The plants were grown in experimental plots at The Blandy Experimental Farm during the spring and summer months of 1940 and 1941. In addition to the above, fixations have been made from the collections of Dr. Leon Croizat at the Arnold Arboretum, Jamaica Plain, Massachusetts. Considering the economic importance of the Euphorbiaceae, it is remarkable that so little attention has been paid to the cytology of the group. Previous workers have largely confined their investigations to the cultivated forms of Aleurites, Hevea, Manihot and Ricinus. Undoubtedly the difficult fixation and the small size of the chromosomes have been important factors in the neglect of the family cytologically. The 2n chromosome determinations *have been made from mitotic metaphases in root-tip and stemtip, material fixed in Belling's modification of Navaschin's solution (Belling, 1930), or La Cour's 2 BE solution (La Cour, 1931), embedded according to La Cour's alcohol-chloroform-paraffin schedule, sectioned at 15 microns and stained in Newton's crystal violet-iodine stain. Stem-tips and young leaves were also fixed in Carnoy's fluid and slides prepared according 'to Baldwin's maceration, aceto-carmine technique (Baldwin, 1939). As has been observed by other investigators on Euphorbiaceous genera, the material proved variable as regards fixation, owing to the copious latex present in most genera, the mucilaginous nature of the roots, and the waxy nature of leaf bud material. Belling's solutions have been used largely for the root-tip preparations. A very satisfactory method for removing mucilage from and reducing surface tension on root-tips is obtained by putting them in the mouth and momentarily bathing them in saliva.

Metabolic activities of roots and their bearing on the relation of upward movement of salts and water in plants

Abstract: THE RELATION of water absorption and transpiration to the'absorption and movement of salt in the plant has been a subject of discussion since an early period in the study of plant physiology. Various divergent views have been expressed. From some researches, the evidence seems to lead to the idea that the absorption and upward movement of salt are often largely independent of the movement of water; while from other researches it would appear that increased transpiration results in enhanced salt' absorption-several recent articles report data interpreted in this way (Schmidt, 1936; Freeland, 1937; Wright, 1939; Phillis and Mason, 1940). Evidence by earlier investigators has been reviewed in the monograph by Curtis (1935). Apparently, most workers have not experimentally studied the role of metabolic factors in salt absorption and upward movement. Previous publications from this laboratory (Hoagland, 1936; Hoagland and Broyer, 1936; Prevot and Steward, 1936; Hoagland, 1940) presented detailed evidence on the absorption and accumulation of salt by excised root systems of the young barley plant. This evidence clearly established the point that the initial process of salt absorption by uninjured roots is not dependent on water absorption and transpiration. We now desire to discuss a series of experiments on intact young barley plants which illustrate the importance of the relations of root metabolism to the upward movement of salt as well as to its absorption and accumulation in root cells of excised roots. The whole subject of salt absorption and movement has many ramifications, and the present paper deals only with a section of the phenomena involved, although it is believed that a point of view is outlined which has general significance. RESULTS.-The first experiment (fig. 1) had for its objective a comparison of the amounts of salt absorbed and transported by metabolically active young barley plants (initially high in sugar and low in salt content) under two extremes of conditions affecting water absorption and transpiration (a) in the dark in a highly humid atmosphere,2 (b) in the light (normal greenhouse illumination) with rapid movement of air produced by an electric fan. The culture media in both cases were controlled at 250C. The duration of the experimental period was twelve hours. Under both conditions of the aerial environment, salt (KBr) was rapidly absorbed, and

Germination and seedling development in five species of cypripedium l.

Abstract: THE EFFECTIVE conservation of our native ladyslippers is in large part dependent upon an understanding of the reproductive habits and the environmental conditions necessary for population maintenance of the individual species. Such information is essential if proper management practices are to be undertaken, and even more essential if it should prove necessary in the future to resort to artificial propagation for the restocking of depleted areas. So far, no practical technique for the production of native ladyslippers by seeds or by vegetative division has been described. Many of the otlher species of niative orchids have been successfully raised from seed, in most cases by use of the general methods originated by Knudson (1922) for tropical orchids. The temperate zolne ladyslippers belong to the genus Cypripedium L. The seedling stages of only one of the twenty-eight known species have ever been described. Thilo Irmisch (1853) gave an excellent account of the seedling morphology of Cypripedium Calceolus L., the solitary member of the genus occurring in Europe. The connected story of seedling development was pieced together by Irmisch from a series of seedlings discovered in the field. The earliest stage described was a protocorm "less than one line (112 inch) long . . . . inverted, short cone slhaped, curved on the underside." It assumed no regular position in the soil, being sometimes vertical, sometimes horizontal. Irmisch stated that neither the protocorm nor the roots possessed root hairs. The first leaf was scale-like, placed just above and usually on the same side as the first root. The elongating stem axis produced four or more nodes bearing scale leaves before the first true, chlorophyll-bearing leaf was produced. All but the first-formed scale-leaf possessed axillary buds. Fuchs and Ziegenspeck (1926) also gave descriptions of seedlings of Cypripedium Calceolus as determined from field-collected specimens. Their account agrees with that of Irmisch in most particulars. They differ in stating that the first root is exogenous instead of endogenous and that root hairs are present. Tropical ladyslippers of commercial importance belong to the distinct genus Paphiopedilum Pfitzer. Their seedling stages were well studied by Bernard in 1909. Their development, in part because of the 1 Received for publication November 9, 1942. Contribution from the University of Wisconsin Arboretum. Jour. Paper No. 3. This study was supported in part by the Research Committee of the University of Wisconsin and in part by a grant-in-aid from the American Association for the Advancement of Science through the Wisconsin Academy of Sciences, Arts and Letters. Special thanks are due Mr. Martin J. Gillen of the Gillen Wildlife Sanctuary, Gogebic County, Michigan, for the many courtesies and material assistance extended during the summers of 19391942. continual growth afforded by tropical conditions, is very different from that of Cypripediumn. Early studies by the author on asymbiotic anid symbiotic germination of native Wisconsin ladyslippers (Curtis, 1936) resulted onilv in the production of initial stages roughly resembling the protocorms described by Irmisch. Continued growth could not be maintained under tlle conditions then employed. It was felt that a knowledge of the enivironmnental conditions under which gerim-ination took place in nature would aid in the selection of methods for artificial germination. Accordingly, a study of seed production, seed germinationi, and seedlinig development of certain of the native ladvslippers was instituted in 1938. METHODS AND MATERIALS. Five species of ladyslippers are included in the study -Cypripedium reginae Walt., C. acaule Ait., C. parviflorum Salisb., C. pubescens Willd., and C. candidutm MNuhl. Seedlings of Cypripedium arietinum R. Br. were foLnd in 1924 in Door County, Wisconsini, in what is now the Ridges Wild Flower Sanctuary, but tlhev were not preserved and, hence, are not included in this studv. Locatiolns and dates of observation for the various species are shown in table 1.

Vessel specialization in the late metaxylem of the various organs in the Monocotyledoneae.

Abstract: PREVIOUS PUBLICATIoNS by the present author concerning vessels in the Monocotyledoneae have considered the occurrence (Cheadle, 1942) of these structures, as well as their origin and specialization (Cheadle, 1943). Inthe latter paper it was pointed out, among other things, that vessel members with simple (porous) perforation plates are the most highly specialized, and that those vessel members with long scalariform plates are the most primitive. Among other observations in the earlier paper, the types of vessel members in each organ were tabulated, family by family. The object of the present report is to amplify the observations on the occurrence of these types of vessels and to present evidence concerning the specialization of vessels within the plant from organ to organ. The specialization within the organs themselves will form the basis for a subsequent paper on vessels. The literature on the subject of this paper, as indeed on all phases of the study of vessels in the Monocotyledoneae, is neither large nor particularly pertinent and needs no review for the present publication. MATERIALS AND METIIODS OF PREPARATION.-Various organs in 306 species of 204 genera in the following thirty-four families as defined by Hutchinson (1934) were used in the investigation.2 The first number within the parentheses refers to the number of genera studied and the second number to the number of species. Agavaceae (9, 13); Alismataceae (1, 4); Alstroemeriaceae (1, 1); Amaryllidaceae (15, 20); Araceae (8, 10); Bromeliaceae (7, 6); Butomaceae (2, 2); Cannaceae (1, 1); Commelinaceae (4, 5); Cyperaceae (10, 31); Dioseoreaceae (1, 3); Eriocaulaceae (1, 1); Gramineae (42, 61); Haemodoraceae (2, 2); Hypoxidaceae (1, 1); Iridaceae (3, 5); Juncaceae (2, 10); Liliaceae (30, 43); Marantaceae (2, 2); Musaceae (1, 1); Orchidaceae (11, 12); Palmae (26, 30); Pandanaceae (2, 3); Pontederiaceae (2, 2); Potamogetonaceae (1, 3); Ruscaceae (1, 2); Scheuchzeriaceae (1, 1); Smilacaceae (2, 6); Sparganiaceae (1, 3); Strelitziaceae (3, 3); Trilliaceae (", 3); Typhaceae (1, 2); Xyridaceae (1, 3); Zingiberaceae (7, 11). It is obvious in the above list that the number of species in the Gramineae is especially large. The Gramineae will, therefore, be treated separately in certain sections of this report so that the effect on the general conclusions of such a large number of species from a

The osmotic and vitalistic interpretations of exudation

Abstract: THROUGH SOME process that involves an expenditure of energy, living cells are able, under suitable conditions, to accumulate and retain solutes against concentration differentials.2 There is no longer a question as to the existence of this metabolic mechanism. Conversely, the view is well established in the minds of a number of investigators that the protoplasm, through some energy-expending mechanism, can expel water (some believe solutes as well) into non-living solutions against a concentration differential. Root pressures and the bleeding of plants are commonly used as examples of the water secretion process, the argument being advanced that the known facts cannot be explained on the basis of osmotic action alone. Whether the supposed expulsion of water from the living protoplasm to vacuolar, xylem vessel, or exterior solutions is designated as metabolic or active secretion, or as vital activity, is a matter of terminology that is largely immaterial to the primary question of whether this unexplained physical or chemical force actually exists. Belief in the existence of such a force has been enhanced, doubtlessly, both by the knowledge that the little understood solute-accumulation mechanism exists andby the fact that the energy expenditure for effecting a given increase in concentration should be the same whether by solute uptake or water secretion. The experimental results presented in this paper support the view that exudation is a purely osmotic phenomenon that follows the loss of solutes from living tissues to the xylem vessels. Certain weaknesses in the evidence advanced to support the water-expulsion theory are discussed. HISTORICAL.-Dutrochet (1837) was the first to regard osmosis as the cause of exudation. This phenomenon, he wrote, is exactly the same as the one that causes a concentrated solution to ascend in the tube of. an endosmometer when one end is closed by a membrane and plunged into water. He believed that the membrane of his osmometer and the living cells of the root tips (spongioles) functioned in the same manner. Pfeffer (1899, p. 271) thought that Dutrochet's explanation was erroneous and credited Hofmeister with first offering the correct interpre1 Received for publication April 9, 1943. The writer is indebted to Dr. Hugh G. Gauch for his collaboration in the collection of data on the exudation of' cotton plants and to Mr. John W. Brown for the chloride determinations reported in figure 5. Cooperative investigations of the Division of Cotton and Other Fiber Crops and Diseases, Bureau of Plant Industry, U. S. Department of Agriculture and the Texas Agricultural Experiment Station. Approved by the director of the latter as Technical Contribution 763. 2 The term concentration differential is probably more suitable than the term concentration gradient for the reason that the latter implies a series of uniform steps. tation, i. e., "active filtration and exudation of water into the interior of the plant." Hofmeister's discussion (1862) concludes with the statement that bleeding depends upon the fact that a part of the water taken from the soil by imbibition of the cell walls and endosmosis of the cell contents is passed into the vessels by pressure which is exerted upon the tissue fluids as a whole by the tension of the parenchyma cell walls and the endosmotic overflow of the cell spaces. Clark, referring in 1874 to the almost universal adoption of the "general principle of osmose," concluded that there were "many difficulties in the way of accepting this charmingly simple hypothesis." He doubted that "any other force than the vital action of the roots was necessary." Wieler (1892), after calling attention to the necessity for oxygen, concluded that the seat of bleeding was in the living cells of the xylem, and that bleeding depended upon the ability of different parts of the cell protoplasm to react unequally to a stimulus. Wieler showed that older root segments would bleed when the lower end was closed, whereas Dutrochet believed that the activity was confined to the extremities of the roots. The "simple osmotic theory of exudation" as stated by Atkins (1916) was supported by Priestley (1920, 1922). Although not included in Atkins' statement, it is evident that any adequately inclusive physical hypothesis of exudation must include the concept of a net differential between the osmotic force (diffusion pressure deficit) in the xylem vessels and the sum of the osmotic and capillary forces in the exterior substrate. There are notably few data in the literature 'that involvelthis comparison. The flow of sap in the spring, when hydrolysis and movement of storage carbohydrates become active, has provided the general example of a correlation between sap concentration and root pressures (see Atkins, 1916; Speidel, 1939). Wieler showed that plants would produce an exudation if their roots were repeatedly warmed, and also that bleeding could in some cases be induced by immersing roots in various solutions (regarded as stimuli) and then returning them to water. No one in recent times has doubted that osmosis is involved in root pressure, and all, with one exception, have agreed that the seat of the osmotic activity is in the dead xylem vessels. Lundegardh (1940) has considered osmosis to be the single cause of static root pressure; but water movement, he believes, is an electro-osmotic activity synchronized with salt uptake. McDougal, Overton and Smith (1929), Renner (1929), Heyl (1933), Grossenbacher (1938), Kramer (1939), and van Overbeek (1942) have all, like a number of others, concluded

The dual phenomenon and sex in hypomyces solani f. curcurbitae

Abstract: IN AN earlier paper,.Hansen (1938) showed that of some 900 isolates of imperfect fungi involving 3 orders, 29 genera and 35 species, over 50 per cent showed the "dual phenomenon," i.e., when they were subjected to single spore analysis, more than half of them were found to be composed of two culturally distinct types, one producing conidia in abundance but relatively scant mycelium, the other developing fewer conidia and more abundant mycelium. These two types were arbitrarily designated as the C (conidial) and M (mycelial) types, respectively. Since that time additional observations have been made on many other imperfect fungi, but especially on isolates of species of Fusarium, of which several thousand cultures have been examined in connection with taxonomic and other studies by Snyder and Hansen ( 1940, 1941a, 1941b). In many of these cultures the M type has been found to arise de novo in the C type with such frequency and regularity that the time of this occurrence could be predicted to within a few days. For example, if a number of single spore cultures were made from the pure C tvpe of the watermelon-wilt fungus, F. oxysporum f. niveum (E. F. S.) S. & H. or the squash root-rot fungus F. solani f. cucurbitae S. & H., it could be predicted with certainty and demonstrated by single spore analysis that the M type would be found in each of these cultures after a period of two to four weeks. In addition to the distinctive cultural appearance, the outstanding character of the M type, in all fungi studied thus far, is its genetic stability. Though the M type may vary somewhat in cultural appearance when it is kept in culture for a long period of time, it has never been found to revert to the C type in spite of numerous attempts to bring about such reversion. M type cultures have been subjected to various normal and abnormal environments of temperature, humidity and light, or grown on many natural and synthetic substrates, or treated with growth substances and vitamins and passed through susceptible hosts, but they have always remained true to type. This extraordinary genetic stability of the M type of all fungi studied constitutes strong evidence that M is a true mutant from C. To prove this contention one would have to demonstrate that M would behave as a unit character in inheritance. For most imperfect fungi such proof cannot be obtained, for the simple reason that they have no known sexual stage. Proof of the genetic integrity of M has, liowever, been obtained for one fungus, namely, F. solani f. cucurbitae, the imperfect stage of the heterothallic fungus Hypomyces solani f. cucurbitae S & H. By crossing M and C strains of this fungus and by subsequent single ascospore analysis, Hansen and Snyder (1940) have demon1 Received for publication February 15, 1943. strated that in inheritance M and C types segregate in the normal 1: 1 ratio. On the basis of the great stability of the M type, and the frequency of occurrence of mutation to this type in many fungi, we postulate that the change of C to M is a true genetic mutation, that it is a unidirectional one, apparently common to fungi in general, and, therefore, of considerable biological (evolutionary) interest. What is the nature of this mutation ? In order to obtain more information on the nature of the M mutant, additional studies were made of its sexual and genetic behavior in H. solani f. cucurbitae. This fungus is composed of two kinds of haploid thalli, usually designated as A and a, which must be brought together to produce the sexual stage. A and a are sometimes referred to as compatibility groups and they may be considered to be analogous if not homologous to the + and used for the compatibility groups in certain Zygomycetes. The normal C type haploid thalli are hermaphroditic, selfsterile and inter-fertile. Each thallus, irrespective of whether it is initiated from a mass transfer, a plurinucleate macroconidium, a binucleate ascospore or a uninucleate microconidium, will always be hermaphroditic. In other words, each haploid nucleus in the C type carries the factors for both male and female. In defining sex in haploid thalli we would say that a female thallus is one that is able to produce receptive structures (perithecial primordia), a male thallus is one that is able to produce fertilizing (spermatial) elements, and a hermaphroditic thallus one that is able to produce both. This latter may or may not be self-sterile. When such hermaphroditic thalli are grown to maturity and have receptive perithecial primordia, then the transfer of conidia from A to a or from a to A will result in fertilization and the production of perithecia. Any part of the living thallus, ascospores, conidia or bits of mycelium can act as the male fertilizing agent. Most Fusaria when isolated from nature occur in the C form, in which macrospores are borne on a sporodochium which is the principal family character of the Tuberculariaceae. In the M type, on the other hand, whether isolated direct from nature or arising de novo in artificial culture, sporodochia have not been observed, and M type Fusaria could for this reason be excluded from the family. It is not, however, to be inferred that we think this should be done. We merely wish to emphasize the necessity of choosing family and other taxonomic characters with great care and only after numerous individuals of the proposed taxonomic unit have been studied in sufficient detail to show their range of variability and general biological behavior. The M type in H. solani f. cucurbitae has not been observed to produce sporodochia or perithecial pri-

Phosphorus transformations during the development of the oat embryo

Abstract: THE DEMONSTRATION in recent years of the fundamental importance of "energy-rich" phosphorus compounds in the metabolism of animal tissues and yeast (Lipmann, 1941; Kalckar, 1942) raises the question of whether similar "energy-rich" compounds occur in plants, and whether they have an essential role in growth and other vital activity. In animal tissues and yeast the key "energy-rich" compound is apparently adenosine triphosphate which stores up the energy released on sugar breakdown and makes this energy available where necessary. This compound, furthermore, where it has been shown to occur, depends for its synthesis on the operation of some kind of fermentation mechanism like the Meyerhof-Emden system, as well as on some types of respiration. The demonstration by LePage and Umbreit (1943) of the phosphorylated intermediates which comprise such a system in Thiobacillus thiooxidans (an autotrophic bacterium which can satisfy all its carbon needs from CO2), together with the presence of adenosine triphosphate suggests that a fundamental phosphorylating system together with "energy-rich" compounds of the adenosine triphosphate variety may be of universal biological significance. Indeed there is some evidence in the literature which indicates that many of the phosphorylated intermediates found in muscle and yeast also occur in some plants and that phosphorylations actually take place (see Tanko, 1936, for an account of such experiments; also Kurssanov, 1941). The oat embryo is of particular interest in this connection, since the oat coleoptile has been the test object for growth experiments involving the auxins, and also because Albaum and Eichel (1943) have shown that there is a change in the character of the metabolism in the early growth stages (prior to 72 hours) as compared to the later stages (beyond 72 hours), fat presumably being the metabolite during early growth and sugar during later growth. Studies were, therefore, undertaken in an attempt to fractionate and identify the phosphorus compounds of the oat embryo, to ascertain whether the character of such compounds changes as the metabolism of the embryo changes, and finally to determinie whether "energy-rich" phosphorus compounds of the adenosine triphosphate variety are present, and how these vary during development. These studies are not yet complete, especially those involving the 1 Received for publication April 1, 1943. This work was done in the Laboratories of the Departnment of Agricultural Bacteriology, University of Wisconsin. The first author wishes to thank Mr. G. A. LePage and Mr. R. Emerson for many helpful suggestions. 2 National Research Fellow in the Natural Sciences 1942-43. identification of all the phosphorus compounds which occur. Nevertheless definite changes in the phosphorus fractions have been found, as well as evidence for high energy phosphorus compounds. These results are presented in the sections which f ollow. MATERIALS AND METHODS.-The essential method in the fractionations is that of LePage and Umbreit (1943). This method, in brief, consists of an intermittent trichloracetic acid extraction of homogenized oat embryos until no more phosphorus is removed and a separation of the combined extracts into several well defined fractions. Each fraction is then analyzed for individual compounds known to occur