506 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
species, since his measurements correspond in the main with those 
of Brefeld’s species. Marchal’s Belgian form, however, according 
to his statement, (’85, p. 42), differed from Dictyostelium mucoroides 
in the fact that the spores were twice as large. But, as will be seen 
by the measurements given above, the great variation in size of the 
spores makes this difference by no means as great as indicated; and, 
although the present arrangement is retained for the present, it may 
prove desirable to unite these two variable species. 
Dictyostelium roseum van Tieghem. 
Bull, de la soc. bot. de France, t. 27, p. 317, 1880. 
“ Spore mass spherical, of a bright rose color. Spores elongated 
oval, 4 /X by 8 ja. On the dung of various animals; especially on 
rabbit dung, in company with Piloholus microsporiis.'^^ France. 
Dictyostelium lacteum van Tieghem. 
Bull, de la soc. bot. de France, t. 27, p. 317, 1880. 
“ The mass of spores forms a milk white drop at the summit of a 
stalk which I have always seen composed of a single row of cells. 
Spores colorless, spherical, very small, 2 fx in diameter. This 
form has been met with several times on decaying agarics.” France. 
Neither of the two preceding forms has been found in American 
cultures, hence the writer can add nothing to our knowledge con¬ 
cerning them. 
Dictyostelium brevicaule Olive. Plate 8, fig. 108. 
Proc. Amer. acad. arts and sci., vol. 37, p. 340, 1901. 
Sorus white; stalks 1-3 mm. high. Spores oval, 3 /x-4 /x by 4 /x 
-7 fji or rarely spherical and 3 /x-4 /x in diameter. 
Dung of sheep and goat. Cambridge, Mass. 
A small, erect fructification, quite constant in the possession of a 
short, rather rigid stalk, bearing a sorus of comparatively large size, 
and very different in aspect from the long, luxuriant, frequently 
flexuous fructifications of P. mucoroides and D, sphaerocephalum. 
Throughout the four years that this species has been kept growing 
in laboratory cultures, it has retained its original distinct characters. 
