20 
THE POTATO FUNGUS. 
others in diluted expressed juice of horse dung, others in expressed 
juice of fresh potato leaves, others upon extremely thin slices of 
potato and on crushed potato mash, others in saccharine fluid, 
others in nitrogen gas, some between pieces of glass kept 
constantly moist, some upon broken tile (also kept constantly 
moist), and 'some upon potato leaves as they grew upon the living 
plant. Besides this I have had a quarter of a hundred of slices, 
kept damp, and under examination every day (almost night and 
day) for the last three months. All these preparations I have 
kept constantly and uniformly moist under darkened bell-glasses, 
for darkness invariably assists the growth of spores of all sorts. 
The first new fact worthy of note is this : many of the resting- 
spores grew in size during nine months of their rest to twice their 
original diameter, or about four times their original bulk, and 
their aspect gradually changed from almost smooth, semi-trans- 
parent bladders to brown, more or less rough and warted or 
echinulate spheres. These latter brown mature bodies were quite 
the same in character with those so sparingly seen last June and 
July. How they arose last year no one saw, but probably the 
wet weather of the early summer caused their appearance. It 
d(ies not follow, because the resting- spores have taken a year to 
artificially mature with me, that therefore they always take a year 
to ripen ; it is quite possible that, in a state of nature and under 
different conditions, they may mature rapidly. At any rate, two 
sorts of bodies were seen together last year, transparent smooth 
bodies, and rough brown ones. I considered them to be different 
states of the same i esting-spores, and subsequent facts have 
proved my supposition to be quite correct. 
The top row of illustrations on Fig. 12 shows characteristic 
conditions of the almost mature reproductive bodies as drawn in 
April last. At a is seen the oospore (or resting-spore) within 
the oogonium (bladder which holds the resting- spore), at b may 
be seen two resting-spores within one oogonium, and at c three 
resting-spores within one oogonium, whilst at d is shown a double 
oogonium — two oogonia coalesced, and each oogonium containing 
a resting spore. 
At the end of April and beginning of May last I began to see 
the first signs of germination, and at this time many of the 
oospores proved effete ; the oogonium cracked at e, or became 
broken into atoms, as at f, discharging a bladder, as at g, which 
perished in fine dust, as at h. 
As the month of May progressed many of the resting-spores 
became dense and dark, with the oospore occupying the whole of 
the oogonium, as at i ; this condition is different from that of the 
body A, for in this the resting- spore, being not quite mature, does 
not yet occupy all the oogonium, hut floats within from side to 
side, as the object happens to be moved under the microscope. J 
shows the contents of oospore being broken up into zoospores ; k 
