THALLOGENS. 265 
In the third mode of germination the spores (Fig. 833, A) 
divide themselves into a certain number of polyhedric portions 
(Fig. 333, 8), which ina short time begin to issue, one after the 
B c 
Fig. 833,—Germination of the Spores in the Potato. 
other, by a round opening (c), thus constituting egg-shape zoo- 
Spores furnished with two unequal cilia; the shorter of those most 
forward, in advance of the corpuscle, and the other dragging 
after it (Fig. 333, p). The movement of these small bodies lasts 
for about half an hour, describing a circle, which gets slower and 
slower until it enters a state of perfect repose. Now that it has 
become immovable, the zoospore takes a regularly rounded form, 
Siying birth on one side to a germ-tube, slender and curved, whicl 
lengthens itself rapidly in water. 
If the zoospores are sown upon the nurse plant, and other cir- 
cumstances are favourable, the zoospores attach themselves te 
the epidermis of its fragments, giving out their usual germ, 
Which after climbing a short time on the outside begins to enter 
4 epidermic cells. Their extremities thus attached soon acquire a 
Considerable thickness, which afterwards increases in a tabular 
form, which perfectly resembles the filaments of the adult mycelium 
y -~ Peronospera, and it soon insinuates itself into the depth of 
the tissues of the hospital plant. 
Tue LicHens. 
ites or Liverworts are cellular plants, requiring free access 
light and air, and of simplest structure. They form irregular 
Patches, more or less dry, according to their exposure upon the 
Surface of stones, trees, and other bodies which they cover, while 
