278 M. H: Hoffniann on Fermentation. 
the vegetation of certain Fungi exerts upon organic liquids, we 
are no longer surprised,” says M. Hoffmann, “at the devasta- 
tions which it causes among plants. We can no longer dispute 
upon the question whether the Fungi are the cause, or a con- 
comitant of these maladies, and we must admit that, under 
certain combinations of temperature, atmospheric condition, &e. 
these effects are due naturally to these Fungi and Infusoria, and 
see in them redoubtable enemies of plants and animals, and 
perhaps also of man.” 
With regard to the potato-disease, M. Hoffmann refers to the 
valuable discoveries of M. Speerschneider, but gives a succinct 
account of the results of his own experiments, from which he 
draws the following conclusion :—After continued heavy rain, 
accompanied by a low temperature and want of sun, Perono- 
spora Solani is developed in prodigious quantity on the leaves of 
the potato plant, and kills them, as.if they had been burnt. 
The mature spores fail to the ground, and, when the moisture 
and heat are sufficient, germinate and send down their filaments 
into the tubers, of which the bark is still tender; the filaments 
reach the interior of the tubers, introduce themselves into the 
cells, of which they decompose the walls and amylaceous grains, 
and thus cause the destruction of the tuber. 
This furnishes the indication of a rational treatment for the 
cure or prevention of the potato-disease. As soon as, under the 
atmospheric combinations above described, the foliage of the 
potato-plants appears to be attacked by a whitish blight (Perono- 
spora), and appears as if burnt, there is danger of rotting of the 
tubers—at least unless dry weather supervene. The best method 
is to cut off the stalks, and it would be well to water the ground 
above the tubers with milk of lime or a solution of chloride of 
lime, or to sulphur it, as has been done with the grapes, with 
the object of destroying the spores of the fungus. 
If the disease has begun to affect the potatoes, it would be 
necessary, before heaping them up, to wash and dry them. The 
remoyal of the herbage appears to be of no consequence when 
the tubers are developed. According to M. Hoffmann’s obser- 
vations, the period of this development, in the part of Germany. 
where he dwells, is seven weeks after the first planting of the 
tubers, fourteen weeks after planting for late potatoes, and 
twelve weeks after planting for spring potatoes. Under any 
circumstances, the removal of the leafy parts towards the end of 
August cannot be prejudicial. 
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