The Circulation Of Sap In Plants In Our Climate,
Especially Of The Graminaceae, Is Not Quick Enough To Yield Much
Moisture.
The African species is five or six times the size of the English.
In the case of branches of
The fig-tree, the point the insects congregate on
is soon marked by a number of incipient roots, such as are thrown out when
a cutting is inserted in the ground for the purpose of starting another tree.
I believe that both the English and African insects belong to the same family,
and differ only in size, and that the chief part of the moisture
is derived from the atmosphere. I leave it for naturalists to explain
how these little creatures distill both by night and day as much water
as they please, and are more independent than her majesty's steam-ships,
with their apparatus for condensing steam; for, without coal,
their abundant supplies of sea-water are of no avail. I tried
the following experiment: Finding a colony of these insects busily distilling
on a branch of the `Ricinus communis', or castor-oil plant,
I denuded about 20 inches of the bark on the tree side of the insects,
and scraped away the inner bark, so as to destroy all the ascending vessels.
I also cut a hole in the side of the branch, reaching to the middle,
and then cut out the pith and internal vessels. The distillation
was then going on at the rate of one drop each 67 seconds,
or about 2 ounces 5-1/2 drams in 24 hours.
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