20 
Journal of Agricultural Research 
Vol. XXIII, No. I 
develop on com meal agar (io p. 225) while with the writer’s they were 
often seen to form in that medium. Finally, the oospores of P. parasitica 
measure from 15 to 20 n in diameter, on an average 18.6 jx, which is very 
much smaller than the writer’s, in which the average is about 25 jx. 
It seems advisable here to call attention to the fact that the measure¬ 
ments given by Rosenbaum ( 21 ) for Phytophthora parasitica differ essen¬ 
tially from the original description by Dastur. By some mistake he 
must have received a culture supposedly P. parasitica but, judging by 
his figures and description, certainly different from that organism when 
compared with the original. A personal examination of both Rosen¬ 
baum’s culture and a true culture of P. parasitica obtained from Sherba- 
koff further establishes this difference and leads to the surmise that the 
culture in question is P. colocasiae Racib. instead of P. parasitica. No 
attempt v, r as made to verify this supposition. 
Phytophthora colocasiae as described by Butler and Kulkarni (5), can 
be distinguished at once morphologically from the rhubarb species. Its 
sporangia measure 38 to 60 /x by 18 to 26 4, that is, distinctly elongate, as 
compared with those of the rhubarb species, which are seldom if ever 
more than half again as long as broad. Its zoospores are very large 
(15 to 18 jx hy g to 12 \x when in motion and 10 to 13 /x when at rest). 
There are only about 20 to the sporangium. The writer’s measure 8 to 
9 /i by 11 to 13 /i and 9 to 10 /x in diameter at rest, and as many as 64 
may occur in the sporangium. With P. colocasiae the sporangia are 
easily detached from their conidiophores, and a portion of the pedicel 
remains attached. In the rhubarb fungus they are very seldom seen 
detached, and never have been observed free, with a distinct pedicel. 
The oospores are about the same in size and similar in manner of develop¬ 
ment. 
Phytophthora cryptogea, Pethy bridge and Lafferty, (19) has oospores of 
about the same size, averaging 25 /x, and likewise the sporangia are practi¬ 
cally the same size, but they lack the apical papillae or at least the papillae 
are indistinct, which constitutes a distinct difference from the rhubarb 
form. In addition, a continuation of the growth of the fungus through 
an empty sporangium, with the formation of a new one either inside the 
walls of the old or just beyond, often occurs with P. cryptogea , whereas 
it has never been observed for the rhubarb species. It is like the rhu¬ 
barb species in being actively parasitic when inoculated into apples and 
turnips but differs in not finding carrots and parsnips equally congenial. 
One strong point of difference is that it reluctantly produces spores of 
any kind. The rhubarb species produces all forms very readily. 
Phytophthora allii Saw. (22), described in 1919 on Allium flstulosum L. 
in Formosa, has distinctly larger sporangia, averaging 49.4 by 36.5 jx, 
which fell off with persistent pedicel, in this respect, too, differing from 
the rhubarb'•species.. 
Phytophthora meadii McRae (15), the most recently described species 
of Phytophthora, has sporangia distinctly different from the writer’s in 
that they are very much more elongate, measuring 33 to 67 by 14 to 28 /x; 
moreover, the scarcity of chlamydospores is emphasized, while with the 
writer’s they are very abundant. 
We now come to Phytophthora terrestria Sherb. (23) and P. melongenae 
K. vSawada (22). In a personal letter from Dr. Sherbakoff dated Febru¬ 
ary 12, 1921, he stated that it was his desire that his organism be referred 
to hereafter as P. terrestris (the former ending being grammatically incor¬ 
rect). Pethybridge and Lafferty (19, p. 497) have stated as their opinion 
