Accordingly, in N. A. S. the latest arrival from Colorado was described as a new species, and with some temerity perhaps, offered as a second species of the hitherto monotypic Leocarpus, all on account of the peculiar capillitium. Sometime after publication our most valued correspondent Mr. Bilgram called attention to the resemblance between the Colorado and Louisiana material already referred to. The University specimens as stated were small, broken, and in every way poor, but enough remained to indicate the evident justice of our correspondent's suspicion. Further investigation of the Holway material in Philadelphia showed that it too was entitled to consideration! Inasmuch as the Holway sending was all from one plasmodium, all difficulties vanished at once. The Iowa gathering showed two phases: one at the University represents P. nitens, physaroid, single-walled; while the Philadelphia part of the gathering corresponds, poorly it is true, but in fact, as now appears, to the form coming in perfection from Colorado; leocarpine in structure, published as Leocarpus fulvus; P. fulvum Lister. Since the combination P. fulvum is already in use, synonym of P. rubiginosum, it seems better to write the name suggested by Ellis; Physarum albescens never having been published, because Diderma albescens, as noted took care of itself.

Since Rostafinski we separate all these physaroid forms chiefly by capillitial characters: capillitial structure separates genera. Physarum diderma is a physarum despite its double wall. And so here Leocarpus was set out by its differentiating capillitium. In good specimens of the present species a large part of the capillitial net is entirely free from lime, so that when the peridium first opens at the summit, sometimes no trace of lime appears; the calcareous deposits are below, and tend to occupy not the nodal intersections as in Physarum, but in large masses involve portions of the net itself, nodes and all, as in Leocarpus. Miss Lister's beautiful figures, op. cit., Figs. 66 and 82, show this very well.

In The Journal of Botany, 52, p. 100, the distinguished author and artist records the discovery of this species in the mountains of Switzerland. She says: "This specimen shows a striking resemblance to Leocarpus fragilis Rost., both in the shape of the sporangia and in the capillitium and spores; but although the color of the sporangia varies in both these species, the walls of P. (L.) fulvum are membranous and rugose with included deposits of lime granules and show nothing of the polished cartilaginous layers characteristic of L. fragilis."

The species is a boundary type at best, and shows again how artificial all our taxonomy is apt to prove, when the number of presentations of some particular type becomes larger.

For these reasons, the present author writes Physarum, and believes the question of identity in a perplexing case fortunately settled.

46. Physarum variabile Rex.

Sporangia scattered, stipitate, sub-stipitate or sessile, about 1 mm. high; regularly or irregularly globose, ellipsoidal, obovate or cylindric-clavate in shape; sporangium wall sometimes apparently thick, of a dingy yellow or brownish-ochre color, slightly rugulose on the surface, crustaceous, brittle, rupturing irregularly, sometimes thin, translucent, covered externally with flat circular calcic-masses falling away in patches; stipes nearly equal, occasionally much expanded at the base, rough, longitudinally rugose, variable in size, sometimes one-third of a millimetre high, sometimes a mere plasmodic thickening of the base of the sporangium; color of stipes varying from a yellowish-white to a dull brownish-gray; capillitium a small-meshed network of delicate colorless tubules with large, many-angled, rounded masses of white, or rarely yellowish-white lime-granules at the nodes; no true columella, but often a central irregular mass of white lime-granules; spores dark violet-brown, verruculose, 9–10 µ.

Pennsylvania. Dr. Rex.

Lister, op. cit., describes a variety, sessile, presenting plasmodiocarpous fructification, from Ceylon, also from Antigua, but there are some doubts as to the identity of these with American sessile and plasmodiocarpous forms. Vid. Jour. Bot. XXXVI., p. 113.