(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 Erijiiiphe 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 Erydphe, 

 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 

 ! ) ihe 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 hyphae 

 are dingy or smoky colored, torulose when dry, septate, simple or branched, 

 bearmg 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 Feronospora, 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 Foltactis, Link, in which case its parasitism 

 on living plants is an anomaly. The conidia germinate in water, often emit- 

 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 hyphse 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, G-eraniums, 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 



