Researches into the Nature of the Potato-Fungus. 
263 
parasite. To what species of fungus the forms which are repre- 
sented in the illustrations, and which occur in the preparations, 
belong, cannot, for the reasons already repeatedly stated, be 
determined ; indeed, the question has no further interest for us 
here. 
9. It is thus apparent that we are not much further advanced 
to-day than we were fifteen years ago in our knowledge of the 
morphological peculiarities of the potato-fungus. The warty 
bodies are possibly its oospores. Should this be indeed the case, 
their appearance in the potato-plant in Europe is nevertheless 
so extraordinarily rare that the question suggests itself whether 
they do not occur more frequently in some other nidus than 
the potato-plant, or in any other climate than our own. That 
they will be regularly found somewhere or other is assumed, 
for our knowledge of the habits of numerous allied fungi makes 
this more than probable. With this interrogation I leave 
the domain of morphology and return to the phenomena of 
adaptation. 
As has already been said (page 247), a metoecia or hetercecia 
in Phytophthora may be considered, not indeed impossible, but 
highly improbable ; and if it should exist, there is no indi- 
cation where to look for it. On the other hand, from the 
analogy of other Peronosporea;, the conjecture readily suggested 
itself that the potato-fungus in continuing its development to 
completion, including the formation of oospores, may make use 
of some species of host other than the potato-plant, or, if of 
it, perhaps in some other climate than ours. I do not exclude 
from this hypothesis an exceptional occurrence of oospores in 
our potatoes in Europe, for we have such a case in Cystopus 
cubicus, already mentioned. 
What this other presumptive and more favourable host plant 
may be, I am as little able to say now as I was fifteen years 
ago. The potato-fungus is often found on other species of the 
order Solanacece grown in gardens, but without presenting in 
them phenomena different from those observed when it grows on 
the potato plant ; and, moreover, it is not so frequent on them 
as on the potato. In Solanum Dulcamara (a species indigenous 
to the British Isles as well as to the Continent), it grows only 
in a starved condition ; it has not yet been observed in other 
•indigenous species. Berkeley has described a case where Phyt. 
infestans occurred on Anthocercis viscosa, a New Holland plant 
of the family of Scroj)hulariace(C, closely related to the Sola- 
naceae. On the strength of this, one might ask whether the 
plant on which the potato-fungus forms oospores may not per- 
haps be one of our native Scrap hulariacea?, say, one of the field 
weeds of the genus Veronica or Linaria. Special investigations 
