S64 PRINCIPLES OF BOTANY, ETC. 
fibres being entirely ligneous, but a new one aps 
pears, and is in fact the young plant. 
§ 299. 
Herbs, however, whether they live one year only, 
as the annual plants, or two years, as all biennial 
plants, become so exhausted by the formation of the 
flower and fruit, that the irritability of their vessels 
becomes much impaired; they therefore become 
quite ligneous, and their root and stem must de- 
cay aiter its fruits are ripened. They may, however, 
be preserved for several years, if their flowers, 
when in the bud, be taken off. ‘The same happens 
a~when their flowers are filled, in which case fecun- 
dation does not take place and no fruit is formed. 
These vessels, therefore, retain that arritability which 
is necessary for their duration, and which would 
have been lost by the wasting of their strength, and 
their fibres become only slowly hgneous. 
§ 300. 
This natural death, however, does not come upon 
all plants in the same manner. It is indeed of a 
double kind. In most plants death ensues as in large 
animals, by induration of the vegetable fibre. But 
in soft Fungi and the species of Boletus it happens 
quite the contrary way. These plants imbibe much 
moisture, which increases when they become older. 
In them no part becomes ligneous, but they die in 
a soft state, from superabundance of moisture, and 
are almost dissolved in it. 
§ 301. 
