THE POTATO FUNGUS. 
21 
shows the zoospores within still more clearly, and where they are 
giving an echinnlate appearance to the bladder within (an appear- 
ance adverted to lately by Mr. Berkeley in a letter to the Gardeners^ 
Chronicle) ; l shows the bladder from within the oospore being 
discharged from the oogonium after the manner of Cystopus, with 
the contained zoospores ; this bladder frequently breaks up into 
dust, as at m, setting the zoospores which are at present quiescent 
free, as at n ; two tails shortly appear on these latter bodies, and 
at a certain period of their growth the anterior cilium, or tail, is 
pushed straight out, as seen at o, the posterior tail then quivers 
with an undulatory movement, and the zoospores sail out of the 
field of the microscope. How long the zoospores live it is difficult 
to say, but probably somewhere between twelve hours and a week ; 
at length they come to rest, as at p, when the tails fall into fine 
dust. Some zoospores burst, and at once perish, as at q, whilst 
others throw out threads of mycelium, r, which threads are 
destined at length to bear the conidiophores of the potato fungus 
in its new generation. The zoospores thus obtained were planted 
on the foliage, and upon thin slices of potato supplied from a 
frame by Mr. Alfred Smee. On these materials they at once 
produced mycelium and small conidiophores, which, without doubt, 
belonged to Peronospora, but as better results were afterwards 
obtained from resting-spores similar to i. Fig. 12, the figures are 
not here engraved. 
The Rev. J. E. Vize, Forden Vicarage, Welshpool, a gentleman 
who has made a special study of microscopic fungi, has had 
some of my living material under examination during the past 
winter and spring, and when the first signs of germination showed 
themselves in my oospores, I wrote him to keep a good look-out 
for results. He wrote me as follows, under date of April 21 : — 
“ My idea certainly is that the oospores are germinating ; bottle 
No. 1 had a thin film on it which developed into a lot of mycelium 
and threads of Peronospora ; ” I, too, observed the same fact in 
London. 
Throughout May the habit of the oospores appeared to remark- 
ably change, for instead of producing zoospores they protruded a 
thick and generally jointed thread, this thread agreeing exactly 
in size with average Peronospora infestans thread. On May 13 I 
observed on the preparations treated with expressed juice of horse- 
dung threads similar to the very long branched thread shown at 
s, s, s. Fig. 12 ; these threads were so long that they traversed 
the entire slide, and 1 could only detect a single septum or joint, 
and frequently none, t, u, v, are characteristic : the fatter ^shoT\ii 
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 
wdth the antheridium (a) attached to the oogonium, and still 
upon its last year’s thread ; x is a germinating oospore with, it 
