Nature and Cause of the Potato Disease. 313 
Plate 8. 
Diseased Cell, from the base of a stem of this year's growth, containing the grape-like fungi 
Botritis infestans. — Power of object glass used, 480 diameters. 
boleti or round-headed, with putrescence. The botritis attacks 
a plant both externally and internally, but its character varies 
according to the situation it appears in. Externally it grows on 
a single stalk, surmounted by numerous sporules or seed-vessels, 
arranged in a mass at the apex. No roots can be perceived, and 
it appears to attach itself only to the mere surface of the cuticle. 
Internally, in the first instance, a shoot springs from a single 
seed, which vegetates, forms a stem, and fructifies. The offspring 
and parent continue together, and new generations rapidly d6- 
velop themselves, the whole being connected together by the 
branches formed of the peduncles. Thus a ramification of stems 
and seeds, that spread in all directions, soon exists, which, as 
seen by the aid of a microscope, suggests the idea of a leafless 
vineyard loaded with fruit. The prolific power of this fungus, if 
viewed as a destructive agent, gives it an appalling character. Its 
minute seeds circulate through the vessels of a plant, and vege- 
tate jn its sap and juices. It adheres to the walls of the vessels, 
throws out its branches, and chokes up the passages, and the 
rapidity of its growth soon enables it to infest all parts. The 
exterior as well as the interior of the vessels are alike the subject 
of its attacks, and no part of an infested plant can long be free 
from its presence. If we observe the minuteness and simplicity 
of a seed of this fungus, and afterwards examine its vegetation in 
a diseased plant, we feel astonished at the fecundity and power 
of so small and apparently weak an object. We perceive that a 
