240 DISEASE OF THE VINE. 



explained ? It appears to me that the cause of the predisposition 

 remains as obscure as the cause of the disease. 



1 have said that I incline to believe that the cryptogam does 

 not produce the disease. My opinion founded on the experiment 

 of inoculation is confirmed by the fact, that, among the numerous 

 observations I have made, I have never succeeded in seeing a 

 single filament of the mycelium of the cryptogam without discover- 

 ing also an alteration in the cellules of the epidermis of the Grape 

 immediately under the cuticular membrane. Such alterations 

 first show themselves in a cellule by a change of colour of the 

 chlorophyll, which from green passes to a pale yellow, the fluid 

 contained thickens and loses its transparency, subsequently crystals 

 are formed, and granulations of various sizes, first of a bay, then 

 of a brown colour. The cellulose, or the membrane which forms 

 the sides of the cell, at the same time thickens and becomes 

 coloured. This organ is now dead, and the lateral adjacent cells, 

 going through the same changes, end also by losing all life. Thus 

 are formed broad dark-coloured spots visible to the naked eye, and 

 which extend even over the whole subcutaneous stratum of the 

 epidermis, when the alteration has commenced at several points 

 at once, and the spots have extended so as to run together and unite 

 with each other. Sign. Adolpho Targioni Tozzetti gave last year 

 to the Academy a very clear account of the changes which took 

 place successively in the Grape, and of the apparent seat of the 

 malady. My observations confirm his; I likewise agree with him 

 that the connection between the fungus supposed to be parasitical, 

 and the organs of the Grape, cannot be established but through the 

 cuticular membrane, which in no one instance, not even immedi- 

 ately over the diseased cellules, is found to be perforated. No 

 sucker can be discovered to proceed from the mycelium and pene- 

 trate into the internal membrane of the Grape. 



When the cryptogam has appeared, its horizontal filaments 

 extend, passing chiefly over the spotted spaces, which circum- 

 stance may be alleged in favour of the opinion that by some 

 invisible communication the fungus exercises some pernicious 

 influence on the Grape ; but, for myself, having put forward the 

 idea that the cryptogam is not the cause of the disease, an idea 

 which is also mentioned by Sign. Brignoli in his learned Memoir 

 on the Crambe, I am disposed to interpret this fact differently, 

 and I say that if the fungus vegetates on the diseased Grape, it is 

 because it there finds the proper aliment for its support. This 

 aliment is most probably derived from the fluids exuding from the 



