PHYSIOLOGY. 275 
and in no-respect like the spinal marrow of animals. 
Nature seems to have provided plants with it on pur- 
pose to deposit in it a store of moisture, that. they 
may not suffer during drought. Hence all young 
trees and shrubs have it, because as soon as they 
grow they want it no longer, the wood being an ex- 
cellent substitute. On the same account we don’t 
find it in water plants, as they very rarely suffer 
from drought; all of them have a hollow stem, 
without any pith. — 
§ 269. 
The gem or bud is the embryo of a future branch, 
and its anatomy, therefore, perfectly coincides with 
the anatomy of the stems and leaves, as they are in- 
closed in it, though very minute. The period of 
their formation diifers in different plants. In cold 
regions the bud is formed in autumn, covered ‘with 
a great many scales, and so prepared for the mild 
spring. In warm and hot regions this is different ; 
there no pernicious frost destroys the blossoms of 
the spring, and cold does not impair the vital power 
of the vegetable creation, therefore no precaution 
was necessary. We see then, the buds unfold 
themselves immediately from the bark into branches, 
without having remained there in the form of buds 
for any length of time. However, here we meet 
likewise with exceptions. Hot climates too, have 
some bud-bearing plants, as well as we in our cli- 
mate possess a few shrubs, especially the Rhamnus 
frangula, which never bud. Each bud unfolds a 
branch with leaves, which at the base of each peti- 
8 ale, 
