Nicaragua specimens not only show a continuous vein-like hypothallus, but have the peridia often confluent, the columellae in such cases confluent, the stipes distinct. Furthermore, the largest spores reach the limit of 12.5 mu, and perhaps the larger number range from 10-12.5 mu, and all are very rough. This corresponds with _D. macrospermum_ Rost., which is distinguished, says the author (_Mon._, p. 162, _opis_), "chiefly by the large and strongly spinulose spores." However, the same sporangium in our Central American specimens yield spores 9.5-12.5 mu, a remarkable range. So that _D. macrospermum_ on this side the ocean, at least, cannot be distinguished from _D. squamulosum_, as far as spores are concerned. A similar remark may be made relative to the form of the columella which Rostafinski, in his figures especially, would make diagnostic. The columella in the sporangia with largest and roughest spores is that of a perfectly normal _D. squamulosum_. 7. DIDYMIUM MELANOSPERMUM (_Pers._) _Macbr._ PLATE VII., Figs. 3, 3 _a._ 1794. _Physarum melanospermum_ Pers., _Roem. N. Mag. Bot._, p. 89. 1797. _Didymium farinaceum_ Schrader, _Nov. Gen. Pl._, p. 26, t. 5, Fig. 6. Sporangia gregarious, hemispheric, depressed, umbilicate below, stipitate or sessile; the peridium firm, dull brown in color, frosted with minute crystals of lime, breaking irregularly; stipe, when present, short, stout, dull black, opaque, arising from a broad base or hypothallus; columella large, prominent; dark-colored, rough above, concave below; capillitium of more or less sinuous, usually dark-colored threads, sparingly branched, and often with calyciform thickenings; spore-mass black, spores by transmitted light pale, purplish-gray, spinulose or rough, 10-12 mu. A well-marked and common species, distinguished by its depressed sporangium and dark-colored, opaque stipe. The latter is usually very short, almost completely concealed in the concavity of the umbilicate sporangium. The columella is dark-colored, forming the floor of the peridial cavity. Persoon first named this species as here. Later on, _Uster's Ann._, XV., 6, he substituted _villosum_ as a more appropriate specific name. Schrader rejects both names given by Persoon as unsuitable, and suggests _farinaceum_. Schrad., _op. cit._, p. 27. New England, Ohio, Missouri, Alabama, Iowa, Nebraska; Europe; probably cosmopolitan. 8. DIDYMIUM MINUS _Lister._ PLATE X., Figs. 4, 4 _a_, 4 _b_. 1892. _Didymium farinaceum_ Schr., var. _minus_, List., _Mycetozoa_, p. 97. 1896. _Didymium minus_ List., Morg., _Jour. Cin. Soc._, p. 61. 1899. _Didymium minus_ List., Macbr., _N. A. S._, p. 89.