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XV. — Note on Mr. W. G. Smith's Discovery of the Rest-Spores 
of the Potato- Fungus. By W. Careutheks, F.R.S., Con- 
sulting Botanist to the Society. 
Since the preceding Report was in print the hiatus in the life- 
history of the potato-fungus has been filled up by the discoveries 
of Mr. W. G. Smith, F.L.S., which has been communicated to 
the Scientific Committee of the Royal Horticultural Society, and 
for which their author has received that Society's gold medal. 
The structure and life of the Peronospora infestans, Mont., as 
found on the foliage, haulm, and tubers of infested potatoes, were 
previously well known and had been frequently described ; but 
the conditions under which the life of the parasite is continued 
from the autumn to the following summer have been the sub- 
ject of frequent, persevering, but hitherto unsuccessful research. 
At the instigation of the Royal Agricultural Society, Professor 
De Bary has renewed his investigations in this direction, and 
has arrived at important though yet unpublished results. So 
obscure has this part of the life of the fungus been that some 
investigators have doubted whether the plant was a true Perono- 
spora at all, and whether the desired information would not be 
discovered in some well-known fungus parasitic on a different 
group of plants from the potato, and whose connection with the 
fungus of the potato disease had not been suspected. 
The importance of Mr. Smith's discovery is all the greater 
that the subject was surrounded with so much obscurity. 
By the help of the engraving prepared for these pages by Mr. 
Siftith himself, and of specimens that Mr. Smith has placed at 
my disposal, I am able to place before my readers the result of 
his addition to our knowledge. 
It was in investigating the new aspect which the disease 
had assumed in some, especially in some American,* varieties 
of potato that Mr. Smith discovered the rest-spores. With the 
view of separating the tissues for more exact examination, he 
placed in water some of the diseased leaves obtained from plants 
grown at Chiswick. He observed that the mycelium grew with 
greater rapidity in the water, and after ten days he found it 
producing a large number of minute spherical bodies of two 
kinds, the one considerably smaller than the other. He further 
observed specimens in which the already known fruits of Pero- 
nospora infestans were growing from the same mycelium as the 
newly-discovered bodies. One of these specimens is drawn 
in our illustration. There consequently remained with him no 
