The Life of the Plant. 179 
The formation of spores proceeds, as has already been © 
mentioned, only under the ordinary normal conditions of 
life; when the conditions are abnormal, they are replaced by 
conidia. ‘Thus, for example, in JZucor Mucedo, the brown 
mould which appears so commonly on rotten fruit, the fila- 
ments of cells break up, when the supply of nutrient sub- 
stances is insufficient, into separate cells which, under 
favourable circumstances, are capable of development into 
perfect plants. Although conidia are so similar and so 
nearly related to spores, it appears nevertheless most con- 
venient to treat them as distinct, from the fact of their being 
morbid products. 
Gonitia may be regarded as a higher condition of 
conidia, and are almost peculiar to Lichens. ‘They are 
usually small groups of cells which are not united with one 
another by any definite law (see Fig. 409, p. 285). 
In gemme the cells are united into regular groups, and 
only in this condition detach themselves from the parent 
plant. They occur especially in the Muscinee. In the 
Hepatic they are developed in special bowl-shaped con- 
ceptacles (Fig. 349) ; in Mosses, on 
the contrary, on the stem, root-hairs, 
leaves, and in short on all parts of 
the plant. 
Special interest attaches to the 
mode of reproduction by means of 
buds. These are larger assemblages 
of dissimilar cells, and are moder- 
ately highly organised germs of new ee ee Tee 
plants, inasmuch as they already LAE polymorpha 
consist of axial and foliar organs. 
They are also not distributed irregularly over the parent 
motion. Their mode of development and of propagation will be ex- 
plained more at length in the systematic section cf the work (see Chap. 
VI. p. 250).—-ED. ] | = 
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