BULLETIN OF THE BUSSEY INSTITUTION. 425 
attenuated, not densely compact, as in the former. The odspores of 
the two species are very much alike. In short, one might almost say 
that P. viticola was P. nivea, with the axis and primary branches 
drawn out, and the ultimate branches contracted. 
It has seemed to us desirable to give at the close of the present 
article an account of the species of Peronospora at present recognized 
in the United States, although we can make but a beggarly display 
compared with European countries. It is natural to suppose that our 
list will be increased as collectors of fungi shall hereafter turn their 
attention more especially to plants of this order. But, however many 
species may be added to the number already known, there can be no 
doubt that the number of individuals is much smaller than in Europe. 
We have found it difficult to secure specimens for class demonstration, 
which is never the case in Central Europe, where, early and late, one 
is tolerably certain of finding several species. P. parasitica, Pers., as 
far as our experience goes, is not common ; and we have never found 
it in company with Cystopus candidus on Capsella. P. gangliformis, 
Berk., is one of our few comparatively common species ; and, unfor- 
tunately for market gardeners, it bids fair to become still more com- 
mon. /. vittcola must, on the whole, be considered our commonest 
species, although P. infestans is periodically very abundant. In this 
connection we would call the attention of our readers to the discovery 
of the odspores of Peronospora infestans by Mr. Worthington: G. 
Smith, in the leaves of American varieties of potatoes, for which he 
has been awarded a gold medal by the Royal Horticultural Society, of 
England. As the results of Mr. Smith’s discovery have lately ap- 
peared in several journals, some of which are accessible to most of 
the readers of the Bulletin, we need only refer them to the “ Garden- 
er’s Chronicle” of July 17, 1875, the “Journal of Horticulture and 
Cottage Gardener,” July 22, the “ Quarterly Journal of Microscopic 
Science,” for October, 1875, where two photographs are given, and to 
the “ Journal of the Royal Agricultural Society of England,” 2d Se- 
ries, Vol. 11, Part II., No. XXII., where a review of the subject is 
given by W. Carruthers, F. R. S. 
VOL. I. 64 
