OLIVE; MONOGRAPH OF THE ACRASIEAE. 
505 
etc., in a state of decomposition. Germany; Russia; England ; 
common in America. 
This very common species is extremely variable in the size of its 
spores and fructifications. The limits of the spore measurements 
as given by Brefeld in his original description have been therefore 
somewhat increased. The sori also, like those of other species of 
Dictyostelium, are quite variable in size, ranging from about 100 fx- 
600 /A in diameter. 
It has been mentioned before in the first part of this paper that 
Coemans (’ 63 ), misled by finding Dictyostelium in close proximity 
with certain moulds, regarded it as a pycnidial condition of Rhizoi^us ; 
his account, moreover, is the first published observation of an organ¬ 
ism belonging to this group of the Acrasieae. 
Dictyostelium sphaerocephalum (Cud.) Sacc. and March. 
Plate 8, fig. 109. 
Aanw. myc. Nederl., 9-10, p. 39, pi. 4, fig. 4, 1885. 
Hyalostilbunt sphaeroceplialimi Oudemans. 
Sorus white; when old, yellowish or greenish white. Stalk fre¬ 
quently veiy long and luxuriant, varying from 2 mm. to 1.5 cm. 
Spores oval, rarely spherical, or sub-inequilateral, 3 /a-5 /a by 5/a-10/a. 
Dung of mouse (common), rat, bird, toad, deer, turtle, muskrat, 
etc. Holland; Belgium ; Liberia; Xew Hampshire; Cambridge 
and Boston, Mass.; Pennsylvania; Florida. 
In the above description, the limits of the measurements of spores 
and of the length of stalks are greater than those given by Marchal 
(’ 85 ), by whom the maximum length of the spore is stated as 8 /a 
and that of the stalk as 5 mm. The measurements of the fructifica¬ 
tions are certainly more variable than indicated by Oudemans (’ 85 ), 
who in his description of this form as a hyphomycetous organism, 
gives 4 /A as the breadth of the spore, by 5 /a-G /a in length. 
Marchal, in founding this species, has evidently utilized his own 
observations as well as the earlier published description of the Dutch 
form, since, as will be seen above, he increases somewhat Oudemans’ 
measurements. Judging from the latter’s description, it is by no 
means certain that Oudemans had a form sufficiently distinct from 
the common Dictyostelium mucoroides to warrant making it another 
