surface, such, for instance, as the common sunflower. Among the plants
which have been successfully employed in the drainage of marshy soil by
transpiration probably the species of Eucalyptus (notably _E_. _globulus_)
are most efficient."[2]

[Footnote 1: Reader in Botany. XIII. Uses of the Forests.]

[Footnote 2: Physiological Botany, page 283.]


4. _Assimilation_.--It is not easy to find practical experiments on
assimilation. Those which follow are taken from "Physiological Botany" (p.
305).

Fill a five-inch test tube, provided with a foot, with fresh drinking
water. In this place a sprig of one of the following water
plants,--_Elodea Canadensis, Myriophyllum spicatum, M.
verticillatum_, or any leafy _Myriophyllum_ (in fact, any small-
leaved water plant with rather crowded foliage). This sprig should be
prepared as follows: Cut the stem squarely off, four inches or so
from the tip, dry the cut surface quickly with blotting paper, then
cover the end of the stein with a quickly drying varnish, for
instance, asphalt-varnish, and let it dry perfectly, keeping the rest
of the stem, if possible, moist by means of a wet cloth. When the
varnish is dry, puncture it with a needle, and immerse the stem in
the water in the test tube, keeping the varnished larger end
uppermost. If the submerged plant be now exposed to the strong rays
of the sun, bubbles of oxygen gas will begin to pass off at a rapid
and even rate, but not too fast to be easily counted. If the simple
apparatus has begun to give off a regular succession of small