( 
262 Researches into the Nature of the Potato-Fungus. 
gular, uneven, and of a very pale brownish-yellow colour. Its 
protoplasm is shrivelled up into a small, round, central body, no 
doubt in consequence of maceration. Some of these bladders 
are still loosely surrounded with a very slender, irregularly 
folded or shrivelled membrane, which alternately approaches 
the bladder or retreats from it. It is only to these bladders 
that the terms oogonia or oospores can be applied ; they have 
as little resemblance to the figures in ' Nature ' (fig. e) and in 
the ' Gard. Chron.' (fig. 19, d) as to the oospores of P. Arenarice ; 
they might rather be compared with the thin-walled oospores of 
Peronospora viticola, or with those of a Pythium. But the pre- 
parations do not enable me to arrive at a certain result as to 
what they really are. 
There might still be some light thrown on this subject, not- 
withstanding all this uncertainty, if it were established that the 
organs in dispute are actually developed on the mycelium of the 
potato-fungus, and produced on its branches. The illustrations, 
however, which I have examined, show the contrary. All the 
threads of mycelium in fig. 13 possess numerous very regularly 
arranged septa. Now, it is true that septa occur in the myce- 
lium of P. infestans, especially when old, but they are always 
isolated and very irregular. So long, also, as the threads vege- 
tate vigorously under water, they are for the most part entirely 
without septa. No botanist could accept a mycelium of the 
structure of fig. 13 as that of a Peronospora, unless the clearest 
evidence for it were furnished from some other quarter. Further, 
in the preparations examined by me I found, as already stated, 
the globules without any connection with mycelium. 
In conclusion, I will state another objection, which, no doubt, 
if it stood alone, would have little weight. Mr. Smith found 
his oospores at an advanced stage of the process of maceration 
and decay of the parts of the potato in water. Now, so far as 
experience goes, the potato-fungus is exceedingly sensitive of 
decay, for as soon as this is developed around it, it speedily 
dies, whether under water or in the air. But on the other hand, 
it is known that many other fungi do not begin to grow till decay 
has appeared. 
In the view of all these considerations I may, though with 
many doubts, accept the warty bodies first described as possibly 
the oospores of P. infestans, but certainly not the forms found in 
the macerated tubers. It however remains, that Mr. Smith has 
described two forms of fungus in the macerated material, both 
different from the potato-fungus, and possibly also from each 
other. No one would have thought of associating them with the 
potato-fungus had they not been found in parts of the potato-plant 
when there was a great desire to discover the oospores of that 
