ly,
to split the labellum of a Cattleya, or of some allied orchis, remove
caudicle from pollen-mass (so that no loose grains are about) and put it
carefully into the large tongue-like rostellum, and see if pollen-tubes
will penetrate, or better, see if capsule will swell. Similar
pollen-masses ought to be put on true stigmas of two or three other
flowers of same plants for comparison. It is to discover whether
rostellum yet retains some of its primordial function of being
penetrated by pollen-tubes. You will be sorry that you ever entered
into correspondence with me. But do not answer till at leisure, and as
briefly as you like. My handwriting, I know, is dreadfully bad. Excuse
this scribbling paper, as I can write faster on it, and I have a rather
large correspondence to keep up.

LETTER 637. TO J. SCOTT. Down, January 21st, 1863.

I thank you for your very interesting letter; I must answer as briefly
as I can, for I have a heap of other letters to answer. I strongly
advise you to follow up and publish your observations on the
pollen-tubes of orchids; they promise to be very interesting. If you
could prove what I only conjectured (from state of utriculi in rostellum
and in stigma of Catasetum and Acropera) that the utriculi somehow
induce, or are correlated with, penetration of pollen-tubes you will
make an important physiological discovery. I will mention, as worth
your attention (and what I have anxiously wished to observe, if time had
permitted, and still hope to do)--viz., the state of tissues or cells
of stigma in an utterly sterile hybrid, in comparison with the same
in fertile parent species; to test these cells, immerse stigmas for
48 hours in spirits of wine. I should expect in hybrids that the cells
would not show coagulated contents. It would be an interesting discovery
to show difference in female organs of hybrids and pure species. Anyhow,
it is worth trial, and I recommend you to make it, and publish if
you do. The pollen-tubes directing themselves to stigma is also very
curious, though not quite so new, but well worth investigation when
you get Cattleya, etc., in flower. I say not so new, for remember small
flowers of Viola and Oxalis; or better, see Bibliography in "Natural
History Review," No. VIII., page 419 (October, 1862) for quotation
from M. Baillon on pollen-tubes finding way from anthers to stigma in
Helianthemum. I should doubt gum getting solid from [i.e. because of]
continued secretion. W