BULLETIN OF THE BUSSEY INSTITUTION. 109 
probability the disease must be considered common all over the 
Northern States. We have never received it from California, and 
whether it is common in the south is still doubtful. In the article 
above named we referred to a second disease of the vine caused by 
Uneinula spiralis, and briefly mentioned the trouble produced in 
Europe by Otdium Tuckeri. . During the past year, the Uncinula was 
more common in Eastern Massachusetts than the year before, but not, 
however, so common as Peronospora viticola. The two fungi not 
unfrequently were found growing together on the same leaf. In the 
West, however, the Uncinula seems to have caused more trouble than 
in the East, and in California it prevailed to such an extent as to have 
seriously injured the vines. We have received specimens from differ- 
ent parts of the West and from Dr. C. L. Anderson of Santa Cruz, 
and Mr. D. Cleveland of San Diego, California. The fungus was so 
common that it was frequently exhibited at agricultural societies, 
where it seems to have generally been called Otidium Tuckert, on the 
supposition that it was the fungus to which that name is applied in 
Europe. As we have had numerous letters asking what is O¢diwm 
Tuckeri, and what is the mould on our grapes, we will devote a few 
words to a description of Unecinula spiralis showing wherein it differs 
from Peronospora viticola and resembles Otdium Tuckert. 
In midsummer and autumn, the leaves and young stalks of both our 
cultivated and wild grapes are covered with the white spots of 
Uneinula spiralis, which look not unlike dust.. The spots are plainer 
on the upper than on the lower surface of the leaves, while the spots 
made by Peronospora viticola are principally on the lower surface of 
the leaf, and look more like frost than dust. The spots grow larger 
and larger until they cover the whole leaf, the young stalks, and the 
berries themselves. A microscopic examination made early in the 
season shows that the spots are composed of white mycelial threads, . 
which branch in various directions, and are furnished at intervals with 
suckers by means of which the fungus is attached to the epidermis of 
the leaf. The diameter of the filaments is about .004 mm., and the 
transverse cell-walls are numerous. It will be at once seen that the 
mycelium of the Uncinula is very different from that of the Peronospora. 
In the former, it is confined to the surface of the leaves, stems, and 
fruit, being attached by little suckers, and frequently divided by cross 
partitions. In the latter, the mycelium pervades the interior of the 
