6 
The “rot moulds” are of this kind, such as the potato mildew, American 
vine disease, tobacco mildew, and man other devastating pests. T 
four centres, which condense and soon become distinctly separated — 
from each other by the growth of a special envelope. Ultimately the — 
membrane of the mother cell is ruptured, and the three or four 
smaller bodies, which have been differentiated in its interior, escape, — 
_ each one furnished at one extremity with a pair of delicate mov le 
hairs, by means of which these little bodies, now termed zoospores, cal 
swim actively in any thin film of moisture upon which they may fall 
Possibly this film may be upon the leaf of a foster plant. In a short 
time all motion ceases, and the zoospores come to f st, the pair 
delicate cilia are absorbed, and a germinating thread is produced, 
through the stomata again into the external air, sometimes si 
sometimes in tufts se are the fertile threads of the mould, ¥ 
8 produce conidium at the ti each of anchlets 
same stages again, and indefinitely multiply the pest. i8 ans . 
represents the ordinary conidial fructification of the mould, by ™* 
spot where there is sufficient moisture for the conidia to be a") e 
tiated into zoospores, and afterwards come to rest an germipal® 
This process takes place in summer and autumn, but there, Birr 
ee by which the pest is disseminated in sprMg- 
: mycelium which flourishes within the substance of t 
et is capable of producing larger globose bodies, chiefly | 
stems, concealed from external view. These lobose odes 
png tsince Sr mostly of a brownish colour, and after develor”™ 
y remain in a state of rest within the stems during the wint®? 
