296 FUNGI. 
enced in its culture. According to these opinions, the vegetation 
of the parasite would be purely accidental, the disease would be 
independent of it, the parasite would be able frequently even to 
spare the diseased organs. Others see in the vegetation of the 
Peronospora the immediate or indirect cause of the various 
symptoms of the disease; either that the parasite invades the 
stalks of the potato, and in destroying them, or, so to speak, in 
poisoning them, determines a discased state of the tubercles, or 
that it introduces itself into all the organs of the plant, and 
that its vegetation is the immediate cause of all the symptoms 
of the disease that one meets with in any organ whatever. 
His observations rigorously proved that the opinions of the 
latter were those only which were well founded. All the altera- 
tions seen on examining spontaneous individuals are found 
when the Peronospora is sown in a nourishing plant. The most 
scrupulous examination demonstrates the most perfect identity 
between the cultivated and spontaneous individuals as much in 
the organization of the parasite as in the alteration of the plant 
that nourishes it. In the experiments that he had made he 
affirms that he never observed an individual or unhealthy pre- 
disposition of the nourishing plant. It appeared to him, on the 
contrary, that the more the plant wa: healthy, the more the 
mould prospered. 
We cannot,follow him through all the details of the growth 
and development of the disease, or of his experiments on this 
and allied species, which resulted in the affirmation that the 
mould immediately determines the disease of the tubercles as 
well as that of the leaves, and that the vegetation of the 
Peronospora alone determines the redoubtable epidemic to which 
the potato is exposed.* We believe that this same observer 
is still engaged in a series of observations, with the view, 
if possible, of suggesting some remedy or mitigation of the 
disease, 
Dr. Hassall pointed ont, many years since, the action of 
fungous mycelium, when coming in contact with cellular tissue, 
* De Bary, ‘‘ Memoir on Peronospora,” in “ Annalcs des Sej. Nat,” 
