76 
Mycologia 
illustrated this species photographically, although drawings would 
bring out the details to better advantage. I have submitted speci- 
mens to the mycologists of the Bureau of Plant Industry and wish 
to record my indebtedness to ]\Irs. Flora W. Patterson, the Mycol- 
ogist in Charge of the Pathological Collections, for information 
and suggestions. She has confirmed the presence of oospores in 
some of the oogonia and was disposed to consider the form iden- 
tical with Peronosporites antiquarius. In review of the state- 
ments of Murray (in the Academy, Nov. 17, 1877), and of Wil- 
liamson and Seward mentioned above, it is obvious that we are 
dealing with a distinct form. Due weight must also be given to 
the enormous time interval between the Carboniferous and Oli- 
gocene, as well as the geographic interval between Yorkshire and 
Mississippi. Moreover the oogonia of the American species are 
more than twice the size of the supposed oogonia of Perono- 
sporites antiquarius. 
Regarding the botanical position of the present form it is clearly 
a Phycomycete and belongs to the group Oomycetes. In the latter 
group I cannot find any family of existing forms to which it can 
be referred other than the Peronosporaceae. It is, of course, 
necessary to consider whether the existing families extend back in 
time some million of years, and on this point I am inclined to think 
the endoparasitic forms have varied but little since they assumed 
their present mode of life in their substantially unchanged environ- 
ment. The Peronosporaceae are commonly thought of as exclu- 
sively endoparasitic in leaves and as exserting their spore-produc- 
ing apparatus into the air through stomata or dissolved cuticles, 
thus producing the familiar downy mildews. A number of forms 
have, however, been observed in which the older mycelial branches 
in rotting tissues swell up and form antheridia and oogonia within 
these tissues and it is a reasonable assumption that Peronospora- 
like extinct genera, which perhaps if they could be studied with 
the facility of existing forms would be referred to extinct fam- 
ilies, have existed in past time. I have therefore proposed the 
generic term Peronosporoides for forms like the present which 
resemble the modern Peronosporaceae and are undoubtedly fili- 
ated types. 
9 Felix, J. Zeitz. deutsch. geol. Gesell., 1894, p. 276, pi. 19, fig. i. 
