126 The Potato Fungus. By Worthington G. Smith. 
dung threads similar to the very long branched thread shown at 
8, S, S, Plate CLII. ; these threads were so long that they traversed 
the entire slide, and I could only detect a single septum or joint, 
and frequently none. T, U, Y, are characteristic : the latter shows 
two septa, which is a common condition at this stage of growth ; 
and all three figures show the protoplasm of the oospore coiled up 
within the walls of the latter. "W shows an oospore germinating 
with the antheridium (A) attached to the oogonium, and still upon 
its last year's thread ; X is a germinating oospore with a thread 
showing the first septum ; and Y shows two germinating oospores 
emerging from one oogonium, each thread showing the first septum ; 
the old male organ (antheridium) is still attached to W, X, and Y. 
The figure at Z, drawn on May 12, is characteristic, and shows 
three septa ; the specimen was sent on to the Eev. M. J. Berkeley, 
who replied : " I found the germinating oospore exactly as you 
figure it. There can be no doubt about the matter." Mr. Broome, 
who was examining similar material of his own, wrote on May 4 : 
" It only remains now apparently to see the Peronospora arising 
from the threads which proceed from the oogonia to prove the 
identity ;" and again on May 20 : "I do not see any attached 
conidia, but the space between the sections of Potato is covered 
with long threads resembling the conidiophorous threads, but I 
could not see any with the spores on them." It may be said here 
that no other known fungus has conidiophorous threads similar 
to those of the Potato fungus. 
At the beginning of May, whilst observing the habit of Fusi- 
sporium and its resting state, I observed typical Peronospora 
infestans growing upon the drier parts of the previous year's 
crushed and decayed leaves ; this observation was confirmed by 
Mr. Yize, who wrote on May 22 : " According to my examination 
the Peronospora grows on the drier parts of the magma. I do not 
observe it growing on the very wet." 
On Plates CLIII. and CLIV. may be seen a collection of resting 
spores before and in the act of germination, together with a number of 
Peronospora threads taken from Potato leaves and tubers previously 
infected with the oospores. A, B, C, and D show oospores in 
which the protoplasm which is destined to produce the new plant 
is coiled up within. At E this coil is seen just emerging. This 
convolute mass is really contained within a thin bladder, and 
sometimes the bladder is expelled, as in Cystopus, from the oogonium 
before the coil unwinds, as at F, G. The thread then emerges as 
shown at H, I, and J, sometimes leaving the bladder free but 
broken, as at K, L. It is rare to see the thread of the new plant 
in connection with the oogonium, as at M, N, though I have so 
seen it, together with the septa many times. The first mycelium 
or spawn of the new plant is seen at 0, 0, 0, and from this the 
