ormally bilateral; just in the same way as we now know
that the radiating star-fish, etc., are bilateral? The case reminds me
of those insects with exactly half having secondary male characters and
the other half female.

(581/5. It is interesting to note his change of view in later years.
In an undated letter written to Mr. Spencer, probably in 1873, he
says: "With respect to asymmetry in the flowers themselves, I remain
contented, from all that I have seen, with adaptation to visits of
insects. There is, however, another factor which it is likely enough may
have come into play--viz., the protection of the anthers and pollen
from the injurious effects of rain. I think so because several flowers
inhabiting rainy countries, as A. Kerner has lately shown, bend their
heads down in rainy weather.")

LETTER 582. TO J.D. HOOKER. June [1855].

(582/1. This is an early example of Darwin's interest in the movements
of plants. Sleeping plants, as is well-known, may acquire a rhythmic
movement differing from their natural period, but the precise experiment
here described has not, as far as known, been carried out. See Pfeffer,
"Periodische Bewegungen," 1875, page 32.)

I thank you much for Hedysarum: I do hope it is not very precious,
for, as I told you, it is for probably a most foolish purpose. I read
somewhere that no plant closes its leaves so promptly in darkness, and I
want to cover it up daily for half an hour, and see if I can TEACH IT to
close by itself, or more easily than at first in darkness. I am rather
puzzled about its transmission, from not knowing how tender it is...

LETTER 583. TO J.D. HOOKER. Down, July 19th, 1856.

I thank you warmly for the very kind manner with which you have taken my
request. It will, in truth, be a most important service to me; for it is
absolutely necessary that I should discuss single and double creations,
as a very crucial point on the general origin of species, and I must
confess, with the aid of all sorts of visionary hypotheses, a very
hostile one. I am delighted that you will take up possibility of
crossing, no botanist has done so, which I have long regretted, and I am
glad to see that it was one of A. De Candolle's desiderata. By the way,
he is curiously contradictory on subject. I am far from expecting that
no cases of apparent impossibility will be found; but certainly I expect
that ultimately they will disappear; for instance, Campanulaceae seems
a strong case, but no