(56) 
upon the smooth-leaf varieties. The Clintons were nearly or quite killed 
by it the last two summers. This seems to be a native American, and has 
often been mistaken for Erysiphe tuckeri, Berk , which constitutes the 
vine disease in Europe, — a mistake which has led to an error and disap- 
pointment in its treatment. Sulphur proves effectual in case of the Erysiphe , 
but it lives upon the surface of the leaf, not in the tissues, as does our 
plant. Notwithstanding the continued failures, cultivators still are known 
who spend their time and money with the sulphur remedy, showing again 
the importance of the knowledge of the species and their habits. But, un- 
fortunately, a practicable remedy is not now known. The condia produce 
zoospores, which swim in water some fifteen minutes, then germinate. The 
oospores are found among the cells of the leaf in autumn. If all the old 
diseased leaves could be burned, a preventive would be attained. 
During the last winter (1874-5) a parasite (Plate I, Figs. 5, 6, 7, 8, 9, 
10, 11) was noticed upon many of the plants in the green-house belonging 
!w the Illinois Industrial University. A few of the diseased leaves being 
taken home for examination, although they were exposed but a few minutes 
in a room with previously healthy window plants, the same disease soon ap- 
peared upon the latter ; — a case of the unwitting distribution of disease 
germs by man. Our real study of this species commenced, however, in 
October, 1876, when it reappeared in both the localities just named. In 
one case a box of earth in which some affected plants grew last year (winter 
of ’75-6) was left dry during the summer and some healthy plants 
replaced in the box in October, 1876. Every care practicable was 
taken to see that these plants were sound and to exclude infection from 
any other source. In a week’s time there was evidence in abundance 
of the same parasite. The conidia are now known to germinate when 
at least one month old, but did they lie dormant all summer? Sup- 
posed oospores were found in the petals of Salvias, and figured (Plate 
I. Fig. 10.) This body is 1-500 in. in diameter, with an apparent hyaline 
reticulated epispore and a yellowish included spheroid. The fertile hyphse 
are dingy or smoky colored, torulose when dry, septate, simple or branched, 
bearing conidia in dense clusters on the sides and tips of the rigid, blunt 
extremities. Conidia oval, pappillate, slightly tinted, 1-1800 by 1-2660 in. 
Believing the plant to be an undescribed Peronospora , it was christened P. 
fumosa ; but later examination, since the figure was made, makes it question- 
able about the so-called oospore being such. If not, the plant may belong 
to the aforetime related genus Poltactis , Link , in which case its parasitism 
on living plants is an anomaly. The conidia germinate in water, often cmit- 
ing two or three tubes. Zoospores not seen. On the leaf the germinating 
tubes run over the surface or penetrate through the cells to the interior. 
In about five days from the sowing, the fertile hyphae appear with their 
conidia. They arise from the stomata or from the external mycelium. 
Sometimes the conidial hyphae do not appear until the leaf or young stem is 
in an advanced state of decay. On some plants only unhealthy or fallen 
leaves appear to be affected. Salvias, Geraniums, Centaureas, Senecios and 
others of diverse orders suffer from its attacks, while as many as twenty 
kinds have been found living or dead with the fungus upon them. Had time 
