On the Potato Disease. 71 
_ Another species Spicaria Solani, is thus described. 
Floccis albis, decumbentibus dense intertextis, ramulis fertili- 
bus vulgo quatuor erectis, sporidiis minimis ovalibus concoloribus. 
Some of these species are only found in the internal cavities 
caused by disease, others in cavities under the skin through which 
they eventually pierce and then expand to a very considerable 
comparative bulk. In one instance and one alone Prof. Harting 
has perceived the formation of a particular fungus within the sac 
of a perfect cell; ordinarily their commencement is on the edges 
of internal cavities among the remnants of destroyed cells. In 
this instance the potatoes were of a particular variety from the 
vicinity of Coblence. The fungus belonged to, the genus Oidi- 
um, (Link,) or Oospora, (Wallworth, ) and was named by Prof. H. 
Oidium violaceum. Its characters are: t 
Floccis ramosis violaceis, fertilibus in sporidia subglobosa sece- 
dentibus. It is therefore quite different from any of the others. 
Von Martius does not appear to have met with this, but he de- 
scribes several other distinct varieties. Payen mentions one of 
the same nature, but of an orange color. 
These fungi seem not to be capable of spreading by infection. 
A large number of experiments were made upon this point ; some 
of their sporules were placed in contact with freshly cut potatoes 
and allowed to remain in contact under favorable circumstance 
for many days; in no case was a fungus of the same species re- 
produced. This would appear to be conclusive, but von Martius 
and Payen, both obtained results of a different character. In 
any case we may conclude that it is not a very easy matter to 
Spread infection in this way. 1} Ae 
When the brown or black liquid matter, which appearing in 
the sacs of the cells, is the first visible proof of disease, 1s placed 
in contact with a freshly cut surface, the disease 1s readily com- 
at about the same time as the fungi. Ordinarily two species are 
observed, Glyciphagus fecularum and Tyrogliphus fecule. Later 
In the disease, a species of Rhabditis sometimes appears of the 
same class as those which are found in vinegar, &c. These are 
only some of the more common varieties which occur. 
Prof. Harting has made a partial chemical investigation of the 
re 
diseased alkaline, with an evolution of ammonia. As might 
