288 FRINCIPLES OF BOTANY, ETC. 
the plant begins to form new radicles in place of the 
old ones. If at this period, in the latter part of 
autumn till the middle of January in our climates, 
a birch or walnut is bored, we get no sap. The | 
tree has sap, but only as much as it just wants, and 
as suffices to form new radicles. Wence fruit-trees, 
which had too much fruit, decay, because their 
strength by the too great waste of sap is exhausted 
If such a tree or shrub has formed radicles, before the 
middle of January, those active young radicles per- 
form their new functions. ‘They imbibe moisture, 
whicly they deposite in the cellular texture, and col- 
Ject in this manner as much sap, as the wasting of it 
by the vegetable powers, which in the next summer 
season are required, makes necessary. If at this time 
a stem is bored, a great quantity of moisture flows 
out, in those plants which receive a great quantity 
of it. But if at the end of January or February, 
the weather becomes mild, this flow of sap ceases 
altogether, and trees when only then bored, give 
nosap. ‘This flows again when the weather becomes 
cold. ‘Those who adhere to the theory of the ascent 
and descent of the sap, say, that in warm weather 
the sap ascended too high, and in cold descended 
too low. This singular change, however, of its 
‘lowing and ceasing to flow, depends on this, that as 
soon as the weather is fine and mild, the transpiration 
in plants goes on with greater rapidity, therefore 
naturally the quantity ef the sap becomes less; on 
the contrary, in cold weather the transpiration 
is not considerable, and therefore the sap accu- 
mulates. 
On 
