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20 MICROSCOPIC PLANTS. [CHAP. 
it speedily ramifies in different directions, and bears 
fruit at the tips of the branches, as at ¢,e,; these fruits 
are termed simple - 
spores, or conidia, 
because from their 
smallness they are 
dust-like. It is 
quite possible they 
may be an early 
"state of the vesicles 
ACE which contain the 
te RG oes Se: penmna > © zoospores, as seen 
Fig. 21. at f, g. However 
this may be, they 
are commonly arrested in growth while still small, 
and they germinate in an exactly similar manner 
with the zoospores themselves, and may be con- 
sidered somewhat analogous with seeds, The Po- 
tato fungus has another method of reproducing 
itself in the ‘swarm spores, as shown at f g. 
These are so called because, on the application 
of moisture (as supplied by rain or dew, or when 
applied artificially), the vesicles set free a swarm of 
from six to fifteen or sixteen other bodies known as 
‘zoospores, so named because they are furnished with 
two lash-like tails, and are capable of moving rapidly 
about like animalcules. This rapid movement usually 
lasts for about half an hour, and (like the dust-like 
conidia, or ‘simple spores,’ before mentioned) the 
Swarm spores generally enter the breathing-pores of 
the leaf, and there germinate. So potent, however, 
are the contents of these bodies when set free, that 
