22 
THE POTATO FUNGUS. 
tliread 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 charac - 
teristic, and shows three septa ; the specimen was sent on to the 
Rev. 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 conidio- 
phorous threads, but I could not see any with the spores on them.” 
It may be said here that no other known fungus has conidio- 
phorous threads similar to those of the potato fungus. 
At the beginning of May, whilst observing the habit of 
Fusisporium 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. Vize, 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.” 
(m Fig. 13 maybe seen a collection of resting spores before 
and in the act of germination, together with a number of Perino- 
spora 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 o, o, o, and from 
this the Peronospora springs direct (when artificially grown) 
almost invariably in a terminal manner. The conidia are not 
mature in any of the s})ecimens here figured; doubtless this is 
because all the plants are more or less abnormal from being grown 
artificially, but still the threads are characteristic of Peronospora 
no known fungus but the one which causes the 
' j)»bi;ai;o disealse has vesicular swellings such as are shown at p. 
Mr. Chas. B. Plowright (surgeon, of King’s Lynn), a gentleman 
who has long studied fungi, has patiently examined some of the 
J liiv^iiiiig pajteJtifrM with which I have been working this spring and 
, j, mid he writes me on May 19 to say : “ I find plenty 
