Showing papers in "American Journal of Botany in 1914"

Plus and minus strains in the genus glomerella

Abstract: Certain species of the Mucorineae, or black mold group of fungi, are composed of two distinct strains, either of which is capable of living by itself and of producing asexual spores, but neither is able alone to produce the zygospores or sexual stage. When the two strains are together, however, and the environment is suitable, the sexual spores are produced abundantly. In the formation of the zygospores, one gamete is produced by one strain and the other gamete by the other strain. In this group of fungi, the strains are very similar; in most cases it being impossible to differentiate between them from a macroscopic or microscopic examination. While these two are without doubt sexual strains, their similarity has made it seem advisable to Blakeslee, who has made a study of many of the forms, to use the indefinite terms, plus and minus, in preference to male and female Outside of the Mucorineae sexual strains in fungi are either very rare or else have not been recognized and it would seem that they are very rare as many unsuccessful attempts have been made to find them. However in the genus Glomerella, which is the perithecial stage of certain species in the form genera, Gloeosporium and Colletotrichum, a condition exists which approaches that found in the Mucorineae. The ascogenous stages of many of the Gloeosporiums and Colletotrichums have been known for a number of years. In some of the forms, as for example the one causing the bitter rot disease of apples, the perithecial stage is rather'common, while in others its development seems to be rare. Yet with all of the forms the perithecia develop very erratically sometimes present in abundance and other times entirely absent. While working on these fungi during the past several years and trying to find out some of the reasons of the erratic development of the perithecia, the writer has constantly had in mind the possibility of sexual strains. Until about three or four years ago, nothing developed which would in the least show that more than one 244

The Role of Winter Temperatures in Determining the Distribution of Plants

Abstract: The investigation of the control of plant (listribution by the various phases of the temperature factor is one of the most important tasks of physiological plant geography, at the same time that it is one of the most backward and difficult. The field is an old one, the first outlines of which were sketched by Willdenow, Humboldt and Schouw. They delimited the great temperature zones of the earth, but in relation to flora rather than to vegetation, in relation to the distribution of species, genera and families, rather than to the great phvsiologically coherent assemblages of plants. To the investigations and explorations of these men and their immediate successors we owe the dictum (which is itself of later origin) that the character of the flora of a region is controlled by temperature, that of its vegetation by moisture. The only temperature datum used by the early plant geographers was the annual mean, and this is still used as the sole criterion in distributional studies by men who prefer that their generalization', should be broad rather than of scientific utility. The gigantic toil of the phenologists between I850 and I890 yielded some results oln the operation of temperature, and gave us a vast accumulation of data of which some real use was made at the time, and to which we may return in future investigations. The men by whom this work was carried on were mostly climatologists, and their efforts were handicapped by the fact that they worked extensively rather than intensively, and that they had not a sufficient foundation of physiological facts upon which to operate. Our knowledge of temperature influences in the distribution of vegetation is fundamentally underlaid by our knowledge of temperature influences on individual species of plants, and the two bodies of knowledge have come from fields of study which are widely unlike in their perspective and methods: from geography and from plant

Some ecological adaptations of certain fern prothallia—camptosorus rhizophyllus link., asplenium platyneuron oakes

Abstract: The part played by the prothallia in the ecological history of ferns has been given but little attention. If the studies on apogamy and related phenomena be left out of consideration the work along this line is very limited indeed. What work has been done may be arranged in three groups, as it has had to do with the increase of growing points by branching of the prothallia or by the production of special proliferations, the influence of light upon the germination of the spore and the development of the prothallium, the influence upon the prothallia of variations of water supply. (A) Goebel (II: I97-2IO) has summed up the findings concerning the vegetative increase of the prothallia of homosporous ferns. Briefly stated there are two general types of growth, thaL which leads to the formation of a more or less regular heart-shaped plant, and that which leads regularly to considerably branched forms. Of the second group the Vittariaceae and Hymenophyllum show a lobular or ribbon-like body which arises by the branching of a simple primary cell plate. In Trichomanes, also of the second group, the prothallium is a mass of more or less branched filaments. With reference to those forms which regularly develop heartshaped prothallia Goebel (II: 203) says: " Young fern plants which have not yet formed typical meristem easily pass over again into the filamentous stage in feeble illumination. . . .In older prothallia this only takes place if they have lost their meristem and are enfeebled by unfavorable environment. Commonly these conditions result in the production of pluricellular shoots." To this last group mentioned by Goebel belong the plants often cited as producing adventitious outgrowths following mutilation in hybridization experiments. This author also mentions a case of proliferation by adventitious shoots from the base of an old prothallium of Osmunda regalis (loc. cit. I: 49). Mote recently several authors have found 477

Some observations on the formation of the capillitium and the development of physarella mirabilis peck and stemonitis fusca roth

Abstract: While examining preparations of Physarella mirabilis with a view to a study of nuclear phenomena, certain observations were made on the development of the capillitial threads so numerous in this species. In view of the fact that Physarella has not heretofore been studied cytologically; and, further, since the formation of the so-called solid capillitium is still a matter of discussion, it seems worth while to publish at this time the results so far obtained. While the study was in progress, some fruiting specimens of Stemonitis fusca were secured, from which supplementary data were obtained. The literature pertaining to the capillitia of Myxomycetes has been carefully summed up by Harper ('oo, 'I4b) and by Harper and Dodge ('14a), so that it is unnecessary to give here more than a brief glance at earlier investigations. Harper, in his papers on the subject, has described thoroughly the formation of capillitium in certain species in which it is distinctly hollow, and was able to corroborate and add much to Strasburger's ('84) earlier account of the process of formation. In his paper on cleavage in a recent issue of this Journal, Harper gives incidentally some data regarding the capillitium of Didymium melanospermum, but does not dwell upon the methods of its formation.

Cleavage in didymium melanospermum (pers) macbr.

Abstract: Many recent papers have confirmed the contention that cell division in the sporanges of algae and fungi is a process of progressive cleavage by surface furrows as against the older conception of simultaneous division by cell plate formation. Still the unique type of cell division by repulsion of the coarser cell inclusions and their heaping up in neutral planes which delimit the oospheres, described by Farmer and Williams (ii) for the oogones of Fucus still remains unquestioned and little has been added to our knowledge of the mechanics of the cleavage process. The older authors were for the most part dominated in their descriptions of spore formation in sporanges, first by the erroneous theory of cell formation put forth by Schleiden, and later by the conceptions of cell plate formation derived from studies on the higher plants. This older literature has been several times adequately summarized and need not be referred to further here (I5, 29). Timberlake (3I) describes the swarm spore formation in Hydrodictyon as taking place by means of furrows which cut in from both the plasma membrane and the tonoplastic surface of the primordial utricle. Klebs's (i8) figures also certainly suggest that the division is a progressive process. Klebahn (I7) speaks of the division of the oogonia in Sphaeroplea as a cleavage and his figure (no. 2) shows furrows cutting up the multinucleated oogone into the eggs. He does not describe the process of division in the antheridia. Swingle (29) has proved beyond question that in Rhizopus and in Phycomyces the cell division consists in a progressive cleavage by which the multinucleated spore-plasm is cut up into the definitive spores. In Rhizopus the furrows originate primarily from the periphery; in Phycomyces they originate largely from vacuoles in the spore-plasm. The process in these forms is similar to that in the sporanges of Sporodinia and Pilobolus (i6) but with striking and characteristic differences.

New species of green algae

Abstract: In the course of my study of the periodicity of occurrence and reproduction of the algae of eastern Illinois during the past several years, a number of undescribed forms have appeared in the collections, of which the following are now sufficiently well known to be described. In accordance with the rules of the Vienna Congress a Latin as well as an English diagnosis is given in each case. Camera drawings from the type material are added together with notes on the relationship and occurrence of each of the new forms. A part of these species have been mentioned in two preliminary papers published by the writer.'

The pyrenoid of anthoceros

Abstract: The single chloroplast of the cells of the gametophyte of the Anthocerotes, with its pyrenoid-like central region, has long been known. Notwithstanding this, detailed descriptions of these chloroplasts and pyrenoids and comparisons with those of the algae, on the one hand, and with the chloroplasts of the liverworts on the other, seem to be lacking. As early as I85I von Mohl (I4) called attention to the fact that there were "wohl 50 bis IOO Amylumk6rner" in the chloroplasts of Anthoceros, but he did not relate them to the starch aggregations to be found in the green algae. The voluminous earlier literature on the morphology of Anthoceros, as far as I can determine, contains only bare mentions of the chloroplasts and pyrenoids. Leitgeb (g) in fact seems to have made no reference whatever to these structures. Schimper (i8) states that the pyrenoids of Anthoceros "zeigten nach Entfernung der Starke durch Verdunklung nur noch corrodierte, unregelmassig eckige Umrisse." His figures I5 and I6 are apparently surface views of entire, living cells and show only diffuse central regions which have no resemblance to the plastids as seen in stained material. Davis (5) in an account of the nuclear division and the fission of the chloroplasts in the spore mother cells of Anthoceros laevis makes no reference to a pyrenoid and nothing in his figures suggests such a structure. He is unable to identify plastids in the archesporial cells and only as these cells become spore mother cells can the single, very minute chloroplast be identified. This chloroplast enlarges rapidly and undergoes two fissions, thus forming the four chloroplasts of the spore tetrad. The large chloroplasts of the mature spores are filled with conspicuous starch grains, becoming thus "storage vesicles of starch. " Campbell (3, 4) has made the most important recent contribution

STUDIES OF TERATOLOGICAL PHENOMENA IN THEIR RELATION TO EVOLUTION AND THE PROBLEMS OF HEREDITY: I. A Study of Certain Floral Abnormalities in Nicotiana and their Bearing on Theories of Dominance

Abstract: When Mendel's law was rediscovered, dominance was considered as essential and as important a principle as segregation. Further investigation soon demonstrated the phenomenon of "imperfect dominance," and still later studies led to a substitution of the " presence and absence" factor hypothesis for Mendel's conception of contrasted character pairs. De Vries (I902), Bateson (I909), Davenport (I9Io), Castle and others look upon dominance as an attribute of the factor or determiner, and according to the last two investigators, variation in dominance, at least in part, is the result of variable potency, or variation in the power of a determiner or factor to express itself in ontogeny. De Vries held the racially older characters to be dominant over the younger, a conception which the last ten years of experimental investigation has not upheld. On the other hand, East (I9I2) and Emerson (I9I2) think of dominance as a result of the activities of one or more specific factors, plus the modifications produced by the whole factorial organic complex (all the other factors concerned in the organism's heredity) and by the external environment (climate, soil, etc.). In other words, under identical genotypical and external environments, the factor A would always give the same expression, no matter how often the experiment was repeated. The chief value of the data which I have to present lies in its bearing on this important question of dominance. The abnormalities concerned are three in number, viz., petalody and pistillody of stamens and that peculiar form of corolla doubling to which ee Vries and others

The origin and development of the lamellae in coprinus micaceus

Abstract: The question as to the origin and method of developmentof the gills in the hymenomycetes still remains unsettled. Certain stages are well known and have been many times described and figured and certain general conclusions are widely accepted. For example, that in many forms the gills arise endogenously and that the relative positions of the stipe, pileus and hymenium are the same in the undifferentiated button as in the adult. On the other hand, the question as to the method of origin of the gill cavity, the direction of growth of the gill rudiments and their relation to the stipe and pileus, the differentiation of trama and hymenium, etc., have never been clearly and adequately described. The older literature has been reviewed by Atkinson (I906) and others, and I will note only such points as bear especially on my own observations on Coprinus micaceus. Schmitz (I842) describes the gill cavity in Agaricus Bulliardi as an annular cavity separating pileus and stipe. The layer of hyphae connecting the outer margin of the pileus and stipe he called the veil or cortina. It is not clear what he means by veil as compared with the peripheral layer found in Coprinus micaceus. Schmitz proposed a theory of development for all pileate species of fungi according to which the organ nearest the substratum in the mature form is the structure first to arise, thus the mycelium precedes the stipe and the stipe the pileus while the hymenophore is formed last. Hoffmann's (I856) description of the development of the carpophore lies at the basis of many of the current accounts of the method of formation of the pileus and hymenium. He describes the young buttons of Agaricus campestris as small spheres which elongate owing to the growth of the interior cells perpendicularly upward. The terminal cells now grow out laterally and then turn abruptly downward. The ends of these hyphae form the lamellae primordia. In a later paper (i86o) he described sixteen further species of Agaricaceae and still later (i86i) he described the development of Coprinus fimetarius. Hoffmann

An account of the cruciate-flowered oenotheras of the subgenus onagra.

Abstract: The so-called cruciate-flowered Oenotheras are those in which the petals are linear or narrowly oblong instead of broadly obovate. The first one which was described, and the only one, in fact, of the subgenus Onagra which has ever received a distinctive name, was called Oe. cruciata by Nuttall, on which account the character of having linear petals has come to be known as cruciateness. The origin of cruciateness is at present a matter of no little interest to geneticists. Some of them hold to the belief, based, it must be said, upon the traditional systematic treatment of Oenothera, that all the cruciate-flowered races either belong to Oe. cruciata Nutt. or else have acquired the character of cruciateness bv hybridization with that species. In this paper the writer records his conclusion that cruciateness has originated inclependently in several lines of descent and that the aggregate formerly called Oe. cruciata must therefore be resolved into several species and varieties. In accord with this conclusion, he has named and defined some of the cruciate-flowered Onagrae which his cultural studies have shown to be constant and distinct. The original Oe. cruciata was found in Massachusetts by Nuttall who sent specimens of it to several botanists. He never described the species himself, and the name was first published as a synonym of Oe. parviflora L., by Seringe.' The earliest description was that of George Don,2 who cultivated the plant in I824 and later characterized it in his General History of the Dichlamydeous Plants, where the name

The effects of acid and alkaline solutions upon the water relation and the metabolism of plants

Abstract: The problem of the physiological water requirement of plants (4) is essentially only a phase of that greater problem,-the quantity of water retained by living organisms, by cells and tissues, under a variety of normal and pathological conditions, or during development and the evolution of succulency (of fruits etc.) in the higher plants. It is clearly evident that an attempt to answer this question should also be a step toward an analysis of the ways and means by which tissues and cells hold their normal or abnormal amount of water, i. e., the forces which are active in the process of absorption and retention of water. Investigators of late years have sought the explanation of the variations in the amount of water absorbed and retained by plants, as well as by animals, in differences in osmotic pressure, and more recently a theory has been proposed to account for it on the basis of the variable "affinity" of colloids for water. The pages that follow concern themselves with a consideration of a few experiments and with the inquiry whether the acceptance of the suggestion here advanced merely necessitates a revision of explanations or whether it adds another to the forces already considered as active in the water relation of plants. A review in detail of the arguments which have been brought for and against the osmotic conception of water absorption by cells (8), or the one from the point of view of the state of colloids (7,I7), seems out of place at this time, since these are questions which on the basis of the facts now available can not be decided as yet. Though probably overrated, the two theories have contributed the experimental data upon which depends much of the fundamental progress of the physicochemical physiology of organisms. The experiments detailed below have been made with the view toward establishing experimentally what importance, if any, hydrolytic reactions may have in determining the amount of water absorbed and retained by plants during germination and growth. That the

The auxo‐thermal integration of climatic complexes

Abstract: Some features of the life of a plant depend so largely upon a simple and uncomplicated enzymatic action, oxidation or other form of energy release, reduction, absorption or hydratation that their course may run parallel to that of a reaction the velocity of which is known and expressible by exponential law. As examples of this may be cited the development of buds or the germination of seeds in which the hyclrolysis of accumulated food-material and the measurable development ensue at a rate in accordance with van't Hof's rule by which the velocity increases two or three times with every rise of temperature of I80 F.2 Many of the more important activities of living matter, however, are the combined expression of a complicated group of reactions, in which the initiating temperature, and the acceleration above it are not identical or parallel, and these may be linked with still others which are not a function of temperature. It follows therefore that the resultant may be one not calculable from known data concerning reaction velocities. This is true of growth, differentiation and of the constructive processes in general, both in a morphogenic and physiologic sense. It is obvious that if we are to make any rational interpretation of the entire effect of temperature upon the organism in any phase of its activity, or during all of its ontogeny a method must be formulated by which the effect of the duration and intensity of the temperature exposure upon the organism may be calculated. Now since this may not be done in terms of the reaction velocity of any of the underlying or component chemico-physical activities our only recourse is to use a resultant standard, one derived from the organism itself. In other

Gliding growth and the bars of sanio

Abstract: By gliding growth is meant the independent elongation or enlargeinent of cells in the growing zone which occurs, as some maintain, during differentiation and radial growth. The bars of Sanio are said to consist of cellulose and pectic materials in the form of bars or imperfect tubes which extend through two or more cells arising from the same initial in a direction at right angles to the plane of division. These bars have been studied chiefly as they occur in the xylem and phloem of trees, but have also been shown to occur in the more superficial cells of woody plants, where they extend parallel to the surface instead of as radii, as is the case with those arising in the cambial zone of trees. The bars arising in the cambium have been brought into discussions to refute the contention that certain cells on arising from the cambium undergo elongation during differentiation, as well as in studies on the phylogenetic relationship of some Coniferae. In investigations into the nature and activity of the cambial sheath the bars have also been used. It seems, therefore, that gliding growth and the bars of Sanio have been of much interest to botanists during many years. The present discussion aims to contribute some concrete evidence on the subject of gliding growth and at the same time to make brief mention of the rela-ted literature.

Some Observations on the Anatomy and Other Features of the "Black Knot"

Abstract: Some three years ago, while I was connected with the department of botany in the New Hampshire Agricultural College of Durham, New Hampshire, I became interested in the study of the "black knot" fungus, Plowrightia morbosa (Schw.) Sacc., which causes the black enlargements on the branches of plum and cherry trees, and from which character the fungus receives its common name. A considerable amount of material was collected from Prunus virginiana L. in that vicinity at intervals of two or three days, from the early part of May until July, and properly preserved for future study. I also made some cross inoculations on the cultivated plum, but as I was called elsewhere soon after this, I did not pursue this part of the work further. I began the study of my material in Professor Thaxter's laboratory at Harvard University about six months after I left Durham, but after sectioning it was found that the material was all too old when it was collected to show early stages of development of the knot, so I abandoned the work for the time being. Upon coming to the University of Wisconsin in the autumn of I91 I, I found that my colleague, Professor E. M. Gilbert, had already begun the study of this fungus, and as neither of us had progressed far at this time, we agreed to divide the work, Professor Gilbert to study the morphology of the fungus while I was to confine my work to the anatomy of the knot itself. The results I have obtained are given in the following pages. Papers dealing with this fungus in a general way are very numerous, probably owing to its wide distribution in this country. Nearly every Agricultural Experiment Station, in the states where this fungus occurs, has dealt with it more or less with reference to methods of eradication and control. Papers, however, on the morphology of the fungus and of the knot itself are very few, owing possibly to the