Read Ebook: The North American Slime-Moulds A Descriptive List of All Species of Myxomycetes Hitherto Reported from the Continent of North America with Notes on Some Extra-Limital Species by Macbride Thomas H Thomas Huston

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PAGE

PREFACE ix

PREFACE TO SECOND EDITION xiii

BIBLIOGRAPHY xv

INTRODUCTORY 1

THE MYXOMYCETES 17

ADDENDA 282

INDEX OF GENERA 289

INDEX OF SPECIES 290

PLATES, WITH EXPLANATIONS 301

CORRIGENDA

On p. 67, last line but one, at the end, read, p. 323.

On p. 344, in explanation figure 2, last word read hour.

PREFACE TO THE FIRST EDITION

Of course, where later investigations have served to obliterate the once-thought patent distinctions between supposed genera or species, it is proper to unite such forms under the older determinable titles and this we have attempted. But wherever in the present work a name has been changed, the name of the earlier author will be found in parenthesis, followed immediately by that of him who made the change, and in general, recent practice, especially as expressed in the rules of the various codes, has determined the puzzling questions of nomenclature.

In arranging the larger divisions of the group the scheme of Rostafinski has been somewhat modified in order to give expression to what the present author deems a more natural sequence of species. The highest expression of myxomycetan fructification is doubtless the isolated sporangium with its capillitium. This is reached by successive differentiations from the simple plasmodium. The aethalium may be esteemed in some instances a case of degeneration, in others of arrested development. In any event in the present arrangement, aethalioid forms are first disposed of, leaving the sporangiate species to follow from plasmodiocarpous as directly as may be.

The artificial keys herewith presented proceed on the same plan and are to be taken, as such keys always are, not as definitive in any case, but simply as an aid to help the student more speedily to reach a probably satisfactory description.

FOOTNOTES:

PREFACE TO THE SECOND EDITION

The first edition of this little book having been exhausted long ago, the writer in this second issue takes opportunity to correct sundry errata, typographical and other, and at the same time to incorporate such new information in reference to individual species and to the subject entire as the researches of more recent years may afford.

To Miss Gulielma Lister, of London, the writer expresses his sense of deep obligation for much assistance in settling difficult matters of nomenclature and identification; it will be found as a result that in most instances the same thing in the two volumes, English and American, appears under the same name. There are still differences; these result in most cases from different points of view, different estimates or emphasis of characteristics in these ever elusive objects.

The present volume is intended especially for American readers and is accordingly particularly devoted to a discussion of species so far reported on the western continent; nevertheless it has seemed wise to include a brief description of some other forms as well, and reference to many extra-limital species now generally recognized will be found here and there in connection with the more extended treatment of related American forms.

At the last moment, nearly all plates and drawings of the first edition disappeared! necessitating a quick renewal of drawings and plates. This may in part explain lack of uniformity, and various minor irregularities sure to grieve the intelligent student.

BIBLIOGRAPHY

The following are the principal works consulted in the prosecution of the investigations here recorded:--

To these may be added the many contributions on the general subject, as these are found in all sorts of current botanical literature; cited everywhere in this volume as occasion offered.

INTRODUCTORY

The Myxomycetes, or slime-moulds, include certain very delicate and extremely beautiful fungus-like organisms common in all the moist and wooded regions of the earth. Deriving sustenance, as they for the most part do, in connection with the decomposition of organic matter, they are usually to be found upon or near decaying logs, sticks, leaves, and other masses of vegetable detritus, wherever the quantity of such material is sufficient to insure continuous moisture. In fruit, however, as will appear hereafter, slime-moulds may occur on objects of any and every sort. Their minuteness retires them from ordinary ken; but such is the extreme beauty of their microscopic structure, such the exceeding interest of their life-history, that for many years enthusiastic students have found the group one of peculiar fascination, in some respects, at least, the most interesting and remarkable that falls beneath our lens.

The substance of the plasmodium has about the consistency of the white of an egg; is slippery to the touch, tasteless, and odorless. Plasmodia vary in color in different species and at different times in the same species. The prevailing color is yellow, but may be brown, orange, red, ruby-red, violet, in fact any tint, even green. Young plasmodia in certain species are colorless , while many have a peculiar ?cru-white or creamy tint difficult to define. Not only does the color change, sometimes more than once in the course of the life history of the same species, but it may be the same for several forms, which in fruit are singularly diverse indeed, so that the mere color of the plasmodium brings small assistance to the systematist. In fact, the color depends no doubt upon the presence in the plasmodium of various matters, more or less foreign, unassimilated, possibly some of them excretory, differing from day to day.

Each sporangium is at maturity filled with numerous unicellular spores. These are usually spherical, sometimes flattened at various points by mutual contact; they are of various colors, more commonly yellow or violet brown, are sometimes smooth , but generally roughened either by the presence of minute warts, or spines, or by the occurence of more or less strongly elevated bands dividing reticulately the entire surface. The spores are in all cases small 3-20 u, and reveal their surface characters only under the most excellent lenses.

The germination of the spores ensues closely upon their dispersal or maturity and is unique in many respects. The wall of the spore is ruptured and the protoplasmic content escapes as a zo?spore indistinguishable so far from an amoeba, or from the zo?spore of our chytridiaceous fungi. This amoeboid zo?spore is without cell-wall, changes its outline, and moves slowly by creeping or flowing from point to point. At this stage many of the spores assume each a flagellate cilium, and so acquire power of more rapid locomotion. The zo?spores, whether ciliate or not, thus enjoy independent existence and are capable of continuing such existence for some time, assimilating, growing, and even reproducing themselves by simple fission, over and over again. This takes place, of course, only in the presence of suitable nutrient media.

Nevertheless the spores of many species germinate quickly simply in water, and a drop suspended in the form of the ordinary drop-culture on a cover-glass affords ample opportunity. In the course of time, usually not more than two or three days, the swarm spores cease their activity, lose their cilia, and come to rest, exhibiting at most nothing more than the slow amoeboid movement already referred to. In the course of two or three days more, in favorable cases, the little spores begin to assemble and flow together; at first into small aggregations, then larger, until at length all have blended in one creeping protoplasmic mass to form thus once again the plasmodium, or plasmodial phase with which the round began. Small plasmodia may generally be thus obtained artificially from drop-cultures. Such, however, in the experience of the writer, are with difficulty kept alive. Hay infusions, infusions of rotten wood, etc., may sometimes for a time give excellent results.

All authorities agree that the myxomycetes have no connection in the direction of upward development, "keinen Anschluss nach oben," if then their only relationship with other organisms is to be found at the bottom of the series only, it is purely a matter of indifference whether we say plant or animal, for at the only point where there is connection there is no distinction.

But why call them either animals or plants? Was Nature then so poor that forsooth only two lines of differentiation were at the beginning open for her effort? May we not rather believe that life's tree may have risen at first in hundreds of tentative trunks of which two have become in the progress of the ages so far dominant as to entirely obscure less progressive types? The Myxomycetes are independent; all that we may attempt is to assert their near kinship with one or other of life's great branches.

The cellulose of the slime-mould looks toward the world of plants. The aerial fructification and stipitate habit of the higher forms tends in the same direction. The disposition to attach themselves to some fixed base is a curious characteristic of plants, more pronounced as we ascend the scale; but by no means lacking in many of the simplest, diatoms, filamentous algae, etc., and it is quite as reasonable to call a vorticella, or a stentor, by virtue of his stipitate form and habit, a plant as to call a slime-mould an animal because in one stage of its history it resembles an amoeba. The total life of an organism in any case must be taken into account. At the outset plants and animals are alike; there is no doubt about it; they differ in the course of their life-histories. The plasmodium is the vegetative phase of the slime-mould. It needs no cell-walls of cellulose, no more than do the dividing cells of a lily-endosperm; both are nourished by organic food and resort to walls only as conditions change. The possession of walls is an indication of some maturity. In the slime-mould the assumption of walls is indeed delayed. Walls at length appear and when they do come they are like those of the lily; they are cellulose. The myxomycetes may be regarded as a section of the organic world in which the forces of heredity are at a maximum whatever those forces may be. Slime-moulds have in smallest degree responded to the stimulus of environment. They have, it is true, escaped the sea, the fresh waters in part, and become adapted to habitation on dry land, but nothing more. It is instructive to reflect that even in her most highly differentiated forms the channel which Nature elects for the transmissal of all that heredity may bestow, is naught else than a minute mass of naked protoplasm. Nature reverts, we say, to her most ancient and simple phases, and heredity is still consonant with apparent simplicity; apparent we say, for as becomes increasingly evident, nothing that lives is simple!

Notwithstanding all the controversy in regard to the matter, the study of the slime-moulds still rests chiefly with the botanists. A simple phylogenetic scheme for thallophytes is offered in the Strasburger text as follows:--

THALLOPHYTA

COLLECTION AND CARE OF SLIME-MOULD MATERIAL

Specimens collected should be placed immediately in boxes in such a way as to suffer no injury in transport; beautiful material is often ruined by lack of care on the part of the collector. Once at the herbarium, specimens may be mounted by gluing the supporting material to the bottom of a small box. Boxes of uniform size and depth may be secured for the purpose. Some collectors prefer to fasten the specimen to a piece of stiff paper, of a size to be pressed into the box snugly, but which may be removed at pleasure. Every pains must in any case be taken to exclude insects. Against such depredators occasional baking of the boxes on the steam radiator in winter is found to be an efficient remedy.

For simple microscopic examination it will be found convenient to first wet the material with alcohol on the slide, then with a weak solution of potassic hydrate, to cause the spores and other structures to assume proper plumpness. A little glycerine may be added or run under the cover if it is desired to preserve the material for further or prolonged study. For permanent mounting nothing in most cases is better than glycerine jelly. As a preparation, the material should lie for some time in H?ntsch's fluid, opportunity being given for evaporation of the alcohol and water. When the material shows the proper clearness and fulness, it may be mounted in jelly in the usual way. Kaiser's formula gives beautiful results. After mounting, the preparation should be sealed with some good cement, as Hollis's glue.

FOOTNOTES:

The following germination periods are furnished by Dr. Constantineanu .

These records are for sowings in drop cultures, in distilled water, kept at temperature of 65?-70? F. .

Pinoy thinks microbes aid in germination .

The plasmodium in this case chances to be red, scarlet, etc.

H?ntsch's Fluid:-- Alcohol 90% three parts Water two parts Glycerine one part

THE NORTH AMERICAN SLIME-MOULDS

The Myxomycetes are,--

The parasitic Myxomycetes affecting plants include but few species, distributed among four genera. All are parasites in the cells of particular hosts; their vegetative phase is plasmodial and their spores are formed by the simultaneous breaking up of the plasmodium into an indefinite number of independent cells. But a single genus need here concern us,--

Parasitic in the parenchymatous cells of the roots of living plants, causing noticeable enlargement of the affected organ, producing at length galls, knots, and various deformities and distortions. Spores spherical, smooth, colorless, 16 u.

This species, typical of forms so far reported in this country, infests the roots of cabbages, and produces a very serious disease of that vegetable. In England the malady has long been known under the names "clubbing," "fingers and toes," etc. The roots affected swell greatly, and at length resemble sometimes the flexed fingers of the human hand; hence the English name. As the disease progresses, the roots speedily rot away, to the serious injury of the leaf-bearing portion of the plant. In badly affected fields, sometimes one-half of the crop is utterly destroyed. Careful search continued through several years has not availed to bring this species to my personal acquaintance.

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