a. This volume is as we see, a descriptive list of the various forms of the Myxomycetes in so far as these have come to the personal notice of the writer.

Each form is designated, as is usual in discussing objects of the sort, by a particular binomial name, followed, in abbreviated form, by the name of the student or author who in describing the form in question used the combination. Thus Stemonitis splendens was first described by Rostafinski, and the name he thus used is applicable to the form he described, wherever found, and to nothing else.

The proper naming of any specimen would thus appear to be a very simple matter. Such, however, is often not the case, particularly where we are concerned with species long familiar to science. Such often have received, at different times, and at the hands of the same author, or certainly of different authors, different names, given for various reasons; so that one who would refer to, or discuss, a single specimen to-day finds himself often in great uncertainty, confronted by a multitude of binomial combinations all thought to refer to the same particular thing.

By general consent, of course, we strive to ascertain the oldest name on the list; the first that is really and clearly applicable, and we write all other names down as synonyms. In this volume a list of synonyms often accompanies the description; precedes it, showing, year by year, the history of the case; an abstract in fact of the title, as at last approved. The preparation of such an abstract is very troublesome, but is believed to be worth the trouble; must be made, indeed, if we are ever in our discussions to be sure that when we speak or write in America, we are dealing with the same thing intended by the man who speaks or writes in England, or elsewhere.

The space occupied in synonymy, is therefore by no means wasted. By and by, if we succeed in establishing a nomenclature on which competent judges can agree, a thing not at all improbable, almost now attained, the lists may gradually disappear as having historical value only.

b. Taxonomy, in any field, is of necessity concerned with history. For his own sake, no student can ignore the thought and work of his predecessors. No man ever sees nature in completeness, nor even the small part of the world to which he devotes attention. He needs every possible assistance, especially the observations of intelligent men. The present author rejoices to acknowledge the assistance found in volumes written in Europe during the last two hundred years. Such men as Persoon, Bulliard, Schumacher, Schrader, Fries, are deservedly famous; they laid the foundations of mycologic taxonomy. No student can afford to miss Elias Fries; his genius, spirit and scholarship entitle him to the recognition and sympathy of every lover of the intellectual life.

c. The considerations just mentioned may, indeed do, sometimes act as a handicap to the American student, for the simple reason that he comes later to the field of time. He must naturally defer to the decision of men in Europe who are supposedly familiar with original types. An American specimen is presumably the same as one occurring elsewhere in similar latitude and environment. It becomes evident after while that only in certain instances is this undoubtedly the fact. The flora of the American continent has been sufficiently disjoined in space and time from Europe to permit extensive differentiation even in these minor forms, so that we have indeed in the groups we study many species, some genera, definitely autochthonous, more it is believed than are now suspected. An attempt to bring a specimen under the terms of a species described in Western Europe is not seldom an error. It becomes evident, as we go forward, that in eastern North America there are forms not only not described in European literature, but really not, part of European flora, not even adventitiously.

d. Many of the more minute species with which this volume has to do are very elusive, very difficult; for one reason,—perhaps in itself sufficient,—because of their minuteness, and consequent apparent paucity. They may be common, but none the less seldom seen. The comatrichas afford an illustration. There are several very small species. C. pulchella, C. laxa, C. ellisii may be mentioned. C. pulchella has been studied nearly a hundred years and has a synonymy accordingly. In 1875 Rostafinski in the material, and among the descriptions, thought he recognized two distinct forms, and went on to give them names; the first in honor of Persoon, C. persoonii, should show an ovate or ovate-cylindric outline with acuminate tip; the second should be truncate and represent a type first described by Berkeley under a name given by Babington, C. pulchella. Berkeley's drawing shows a sporangium with tip acuminate! Lilac or violaceous tints attracted attention in the spores of C. persoonii only; in C. pulchella all is ferruginous. Curtis is especially commended for noticing the fact in describing S. tenerrima, here included as we see.

Comatricha gracilis Wing. is slender, cylindric and has small spores hardly reaching 6 µ; should perhaps be now set out as a separate species; it is evidently purely an American phase.

Our figures, Plate XII., 16 and 16 a, 18 and 18 a, show C. pulchella and C. gracilis, respectively, extremes. Plate XIII., 4, shows an ovate form not very unusual. This and C. gracilis occur on living leaves.

C. ellisii is another of this minor series, very constant in its delicate beauty, but approaches C. nigra rather than the others here discussed.

C. laxa, as the name implies, shows an open construction, suggested, perhaps, by Rostafinski's photographic print, but better brought out by Celakowsky, Myx. BÖhm., Tab. 2, Figs. 7 and 8.

e. It has been shown[40] that the process of cell-division in the spore-plasm of the myxomycete is not dissimilar to that obtaining under the same conditions in higher plants. On this supposition we have explanation of spore-division in Ceratiomyxa and can understand the adherence of spores now and again notable. Once the latter phenomenon was thought peculiar to the genus Badhamia; but the unsculptured epispore of the spores of reticularias, tubiferas, etc., suggest the same thing and more recently we find it in Dianema and in the StemoniteÆ; even Stemonitis arrives with clustered spores in groups of four, and we are in sight of a generalization wide.

It is interesting to note that something of this sort was observed by at least one student long ago. Schumacher, Enum. Pl. Sell. 2, p. 215, describes Arcyria atra with the characters of an enerthenema, and says "the capillitial threads are some of them diffuse and bear spermatic globules"! Did he anticipate E. berkleyanum? See the text under that species at p. 190, supra.

f. In a paper read December, 1920, before the Mycological Division of Section G., A. A. A. S., the present writer discussed briefly the physical principles involved in some of the more striking peculiarities of the slime-moulds.

It is argued in that paper that the shaping of stipitate sporangia which is so surprising as relating to the ordinary behaviour of fluid masses, as usually observed, is, in part at least, referable to certain well known properties of fluids generally. For this discussion those interested are referred to the article itself in the November number of Mycologia (N. Y.).

Sufficient to say here that it is a fact, in many cases, that in stipitate fructification, so far as observed, the stipe is first to take form, and, as viewed by the writer, in many cases, as it rises, becomes more and more a most delicate but definite ectosarcate capillary tubule, by which ascends the spore-plasm of the point concerned, to such level as may meet the immediate conditions of pressure, of whatsoever source.

It will be interesting in this view to note the resultant shapes as presented in the sporangia of various genera. One may examine for illustrations Figs. 1, 3, 4, 7, Pl. XX., with the thought in mind that the stipe in each case may have served as a capillary tubule to carry up the spore-plasm to the position in which the spores at length are found. In some species of Hemitrichia, for instance, there are spores or spore-like cells found at maturity in the hollow stipe. In other cases the stipe contains refuse matter.

The capillary theory may not, probably does not, play part in every case. It would seem that a stemonitis, for example, must owe the rise of the spore-plasm to the play of different machinery. Brefeldia, p. 154 above, may offer suggestion.

g. On page two of the introductory section of this volume mention is made of the variety of colors shown in the vegetative phases of the organisms we study. This fact is patent to all observers; but the identity of the plasmodium making the display must be ascertained by painstaking or prolonged and repeated observations. This for the reason that, as I am convinced, only in comparatively few cases is the color unchanged during the life-history of a given fructification. It may sometimes change from hour to hour as development proceeds. The color designated in the descriptive pages of this work is presumably, unless as otherwise set out, that immediately preceding that of the maturing fruit.

As suggestive, and as, it is hoped, contributory to better knowledge of this phase of our subject a list of species is here subjoined as presented by my colleague, Professor Morton E. Peck of Oregon, who has given unusual attention to this particular investigation.

h. In a few instances references to illustration do not find place in connection with the descriptive matter. One phase of Physarum albescens is figured on Pl. III.; Mucilago will be found portrayed on Pl. VII.; Physarum viride on Pl. VIII.

j. The group before us has research possibilities not a few. The question of their nutrition and its limits in respect of variety, is yet to be solved. From present indications all that can be said is to the effect that a pabulum similar in variety, no doubt meets the needs of many species. Whether in artificial culture a single base as gelatin or agar would suffice for all or several is yet to be discovered.

Whether a species brought from spore to maturity on artificial diet would conform in any reasonable way to our dim concept of its identity is also, it would seem, a problem. The variation in the field would seem to make it doubtful.

From the table immediately preceding it is plain that there is place for doubt. Color it is surmised is of itself everywhere incidental; the structure, which maintains identity or the reverse, lies deeper, although color may be none the less, in some way a resultant, and therefore in so far a reliable taxonomic guide.

The treatment of our subject so far by no means exhausts the possibilities of even the simpler phases of microscopic study. We have endeavored to appreciate the work of those who hand us the literature of the group, and to recognize what such keen-eyed men have seen; but in our western and southern forests there are probably double as many species, as species go, as we have listed.

The entire group is, as it would seem, in highest measure worthy of investigation and comprehension, and should it at any time prove that to such accomplishment the present volume may have been in any smallest way contributory, the author's satisfaction will be complete indeed.