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.