288 OBSERVATIONS ON THE VINE MILDEW. 



upon which the mould is successively developed. The paren- 

 chym, which corresponds with these specks, is equally brown 

 and less filled with juice than that which surrounds it ; if at 

 this time it were covered with or traversed by mycelium, one 

 ought to find it ; but this is not the case. At a later period the 

 epidermis is frayed, the parenchym dries up, and, after having 

 lived some time, the fungus disappears. 



When the staliv is diseased through its whole extent, the 

 grapes entirely perish ; when the malady attacks the berries in 

 tlie first stage of development, they dry up or fall ; if, on the 

 contrary, they have acquired a certain size, they are able to resist 

 it ; some crack, split, and expose their seeds ; others are de- 

 formed and arrive at maturity, but they never acquire the size 

 which they would have done had they not been diseased. Like 

 fruits v/hich have been punctured by insects, they appear to me 

 to ripen before otiier grapes ; but they are rather fleshy than suc- 

 culent, and they are almost destitute of flavour. 



Another question wliich preoccupies many minds is that of 

 contagion. I avow beforeiiand that I have no belief in it. Ac- 

 cording to my views the fungus does not propagate the malady, 

 but the primitive derangement of the tissues of which I have 

 spoken is endemic. It is the same with the potato disease. It 

 is impossible for us, notwithstanding the numerous researches to 

 which that malady has given rise, to say to what cause it is due. 

 To prove the existence of contagion we ought to be able to produce 

 at our pleasure the disease of the tissues ; but we cannot do so. 

 People, to prove contagion, say that they have placed a sound 

 grape by the side of one which was diseased, and that on the 

 moiTow or the day after the two grapes were equally bad. Tiiis 

 experiment, whicli I have repeated myself many times, and which 

 has always succeeded, may be interpreted in two ways : first, we 

 may have placed by the side of a diseased grape anotlier in which 

 disease iiad already commenced, or wiiicli was predisposed to 

 contract it ; and secondly, the ea.se with which moulds are deve- 

 loped causes tiieir spores when dispersed to germinate and fructify 

 on almost all kinds of bodies provided their evolution be favoured 

 by moisture and temperature. In tliis case tlie remarkable cir- 

 cumstance is, that the points of the fruit or leaves on which the 

 moulds are developed do not present the brown spots. Those 

 who last year attentively followed the pro2:ress of the vine 

 disease, have remarked that it had an exacerbation which lasted 

 till the I5th of August. This I'elapse, tliough real, had no de- 

 structive consequence ; it was the result of the torrents of rain 

 which fell on the 6th of August; its violence had cleansed the 

 grapes and the leaves, but in the following days the spores which 

 had been disseminated germinated ag-ain. As the disease was 



