HORTICULTURAL JOURNAL. 215 



cies cannot be made in a satisfactory manner, for its two other organs of 

 reproduction are insufficient to distinguish it from a great many other con- 

 generous plants, possessing identical organs.* 



If the fungus on the Vine is an Erysiphe, we need not be surprised at 

 the damage which it does. Erysiphes are all true parasites ; f and they 

 always cause diseases more or less serious in the plants which nourish them. 



No one is ignorant of the injurious effects produced by Erysiphe Humuli 

 on the Hop, or how prejudicial E. bicornis is to the Maple, as well as E. 

 clandestina to the common Hawthorn, and E. Pisi to late Peas, &c. 



The disease usually called the mildew, so formidable to the Peach tree, 

 is apparently caused by nothing else than Erysiphe pannosa, a species which 

 is also prejudicial to the Rose tree ; this mildew is likewise richin conidia, 

 pycnidia, and sporangia. There has never been any hesitation, so far as I 

 know, in attributing to these various Erysiphes the atropry, the organic 

 malformation, and the sterility with which their victims have been afflicted ; 

 wherefore, then, should the Erysiphe which attacks the Vines be less capa- 

 ble of inflicting injury than its fellows, and why should we seek to explain 

 otherwise than by its action the disorganization of the Vines thus attacked? 

 If the Vines were supposed to be diseased before the appearance of the 

 parasite, the same supposition, notwithstanding its improbability, must be 

 made not only in the case of all the other plants, wild or cultivated, which 

 nourish Erysiphes, but also as regards those at whose expense Uredo, Usti- 

 lago, Rhytisma, and a host of other parasites live. 



It may undoubtedly be admitted that these do not attack indiscriminately 

 all the individuals of the species on which they live, and that the physiolo- 

 gical condition of the individuals, varying with age, situation, seasons, and 

 other circumstances, exercises some influence in the development of fungi ; 

 but this general proposition, which would in several repects be justified by 



* To whatever species of Erysiphe the one which lives on the Vine be referred, its barren- 

 ness in ascophorous fruits cannot be a special character ; for several are known, such as E. 

 Martii, E. communis, E. lamprocarpa, &c, which are frequently the same in this respect, 

 either owing to the plants which bear them, or the situations where these plants are growing, 

 or to other circumstances which have escaped our observation. 



f It will be readily understood that, among several species, the filaments of the mycelium 

 are provided with small rounded appendages, which are probably organs of suction. We have 

 more especially observed them in Erysiphe Martii, and in E. communis. M. Gaspnrini, and 

 afterwards M. Mohl, have seen several such in the Vine mildew, where, in fact, they can be 

 readily found. 



