238 DISEASE OF THE VINE. 



Having cleared up this point, there yet I'emains the most 

 important question. Is the cryptogam the cause or the conse- 

 quence of the disease of the Grape? I have not the presumption 

 to solve this difficult problem ; it would be necessary to have data 

 more evident, more incontestable, and more detailed, to establish 

 any undeniable demonstration. I will only state, that I am for 

 various reasons disposed to adopt rather the opinion that the 

 appearance of the mildew is ow'ing to a morbid change which the 

 Grape has previously suffered. 



Last year I collected bunches of grapes branches of Vine, 

 leaves of gourds, roses and chrysanthema, all covered with their 

 respective mildews, and shut them all up in a wooden box, with 

 the intention of scattering in the following spring, over healthy 

 individuals of different kinds, the reproductive sporules which it 

 was to be presumed existed amidst the mycelia, and thus, as it 

 were, to inoculate the disease, The experiment was carried out 

 in June this year without producing any cryptogam. It might 

 be supposed that the spores had lost their vegetative powers by 

 too lengthened a state of desiccation. I therefore repeated 

 the experiment in the month of July, making use of fresh 

 mildews which had appeared naturally ; the result was the same, 

 the healthy grapes were not attacked. From this it would follow 

 that the mildew does not produce the disease, or at least that one 



of development, that is to say, the sterile state with moniliforin filaments, 

 the fructiferous state like that I have described, and lastly, another fruc- 

 tiferous state, such as understood by Sig. Bereuger, The finding even of 

 the three states visible at once on the field of the microscope would not be 

 sufficient to support the opposite doctrine ; it would be necessary to 

 prove distinctly the origin of each — for it is not an uncommon occurrence 

 that several of these productions are found so intermingled together as to 

 appear at first to arise from a common mycelium. 



In Fig. 5, magnified to 230 diameters, is to be seen a conceptacle of the 

 Erysiphe communis taken from a leaf of Convolvulus arvensis, on which I 

 found at the same time the other cryptogam with a fructification analogous 

 to that of the Grape. I say analogous and not identical, because some 

 slight differences are observable which might constitute a variety. There 

 also may be varieties which I have observed to fructify in such abundance 

 on Chrysanthema, on Clovers, on Chicory, on the Plantago major, on 

 Artemisia campestris, on Lucern. On all these plants, excepting on the 

 Chrysanthema I have likewise observed the different species of Erysiphe 

 which are peculiar to them, and which are well known. On the Chrysan- 

 thema I could never discover a single conceptaculum which gave any 

 indication of the Erysiphe. So, on the other hand, on the Acer campestre, 

 on which the Erysiphe abounds, I never succeeded in finding any sporangia 

 analogous to those of the cryptogam of the Grape. (This figure 5 is not 

 reproduced here, no one in this country supposing Oidium and Erysiphe to be 

 identical.) 



