ir upper
surfaces closely appressed to the lower surfaces of the leaves of that
side.

This Phyllanthus agrees with Cassia not only in its manner of sleeping,
but also by its leaves being paraheliotropic. (687/2. Paraheliotropism
is the movement by which some leaves temporarily direct their edges to
the source of light. See "Movements of Plants," page 445.) Like those of
some Cassiae its leaves take an almost perfectly vertical position, when
at noon, on a summer day, the sun is nearly in the zenith; but I doubt
whether this paraheliotropism will be observable in England. To-day,
though continuing to be fully exposed to the sun, at 3 p.m. the leaves
had already returned to a nearly horizontal position. As soon as there
are ripe seeds I will send you some; of our other species of Phyllanthus
I enclose a few seeds in this letter.

In several species of Hedychium the lateral halves of the leaves when
exposed to bright sunshine, bend downwards so that the lateral margins
meet. It is curious that a hybrid Hedychium in my garden shows scarcely
any trace of this paraheliotropism, while both the parent species are
very paraheliotropic.

Might not the inequality of the cotyledons of Citrus and of Pachira be
attributed to the pressure, which the several embryos enclosed in the
same seed exert upon each other? I do not know Pachira aquatica, but
[in] a species, of which I have a tree in my garden, all the seeds
are polyembryonic, and so were almost all the seeds of Citrus which I
examined. With Coffea arabica also seeds including two embryos are
not very rare; but I have not yet observed whether in this case the
cotyledons be inequal.

I repeated to-day Duval-Jouve's measurements on Bryophyllum calycinum
(687/3. "Power of Movement in Plants," page 237. F. Muller's
measurements show, however, that there is a tendency in the leaves to be
more highly inclined at night than in the middle of the day, and so far
they agree with Duval-Jouve's results.); but mine did not agree with
his; they are as follows:--

Distances in mm. between the tips of the upper pair of leaves.

January 9th, 1881 3 A.M. 1 P.M. 6 P.M.
1st plant 54 43 36
2nd plant 28 25 23
3rd plant 28 27 27
4th plant 51 46 39
5th plant 61 52 45
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