416 BULLETIN OF THE BUSSEY INSTITUTION. 
same Oidium has been reported in several places in this country; but, 
inasmuch as Oidium Tuckeri is the general name given to any white 
mould on grapes by those of our botanists who have not made a 
special study of fungi, the information is not always trustworthy. Un- 
doubtedly a form undistinguishable from the Otdium Tuckeri of 
Europe does occur in this country,* but to what extent is uncertain. 
During the past summer, the grape-vines at Amherst, Mass., were 
attacked by a fungus which was supposed to be Oidium Tuckeri, and 
which was distributed as such. The fungus was the Uneinula spiralis 
of Berkeley and Curtis, of which the conidia are almost, if not quite, 
identical with Oidium Tuckeri. Perithecia were abundant on the 
specimens we have examined, and the connection between conidia and 
perithecia could be traced. We are not aware that the perithecia of 
Uncinula spiralis have ever been found in Europe, and it is doubtful 
whether the fungus of the European vines is really that species. At 
any rate, it must be admitted that, as used in this country, the name 
Oidium Tuckeri is somewhat indefinite, and does not necessarily refer 
to the same fungus as in Europe. Whatever forms may, correctly or 
incorrectly, be included under Ocdium Tuckeri, as far as our experi- 
ence goes, none of them is by any means as common, certainly not in 
New England, as another fungus, Peronospora viticola, B. & C., which 
is limited to the leaves and stems, and does not attack the fruit. This 
fungus is peculiar to America, and we have attempted in the following 
pages to give a history of its development. 
Although extremely common, the fungus in question is not one very 
likely to attract the attention of those not somewhat interested in 
fungi. It first appears on the under surface of the leaves, which, in 
most of our native species of Vitis, is so covered with whitish wool 
that the fungus, which is of nearly the same color, escapes notice. 
Later, it causes a curling and drying up of the leaf, which then passes 
for any ordinary dead leaf. The fungus makes its appearance about the 
first of August; and, at any time from the middle of the month until 
frosty weather sets in, one can be almost certain of finding it. As we 
* In the Curtis Collection the only American specimen of Oidium Tuckeri 
is one marked 3723 on Vitis rupestris, Texas, Lindheimer. No. 38610, Michener 
(538) on Vitis Labrusca, Pennsylvania, 1851, and Nos. 292 and 399 Russell, 
Mass., September, 1856, on cultivated grape-vines, are the original specimens 
of Uncinula spiralis, B. & C.; and a figure of the asci and appendages is given 
in Berkeley’s “ Introduction to Cryptogamic Botany,” p. 278, fig. 64. 
