d at the number of interesting points which you observe. It
is quite curious how, by coincidence, you have been observing the same
subjects that have lately interested me.

Your case of the Notylia is quite new to me (673/1. See F. Muller, "Bot.
Zeitung," 1868, page 630; "Fertilisation of Orchids," Edition II., page
171.); but it seems analogous with that of Acropera, about the sexes
of which I blundered greatly in my book. I have got an Acropera now in
flower, and have no doubt that some insect, with a tuft of hairs on its
tail, removes by the tuft, the pollinia, and inserts the little viscid
cap and the long pedicel into the narrow stigmatic cavity, and leaves
it there with the pollen-masses in close contact with, but not inserted
into, the stigmatic cavity. I find I can thus fertilise the flowers, and
so I can with Stanhopea, and I suspect that this is the case with your
Notylia. But I have lately had an orchis in flower--viz. Acineta,
which I could not anyhow fertilise. Dr. Hildebrand lately wrote a paper
(673/2. "Bot. Zeitung," 1863, 1865.) showing that with some orchids
the ovules are not mature and are not fertilised until months after
the pollen-tubes have penetrated the column, and you have independently
observed the same fact, which I never suspected in the case of Acropera.
The column of such orchids must act almost like the spermatheca of
insects. Your orchis with two leaf-like stigmas is new to me; but I
feel guilty at your wasting your valuable time in making such beautiful
drawings for my amusement.

Your observations on those plants being sterile which grow separately,
or flower earlier than others, are very interesting to me: they would be
worth experimenting on with other individuals. I shall give in my next
book several cases of individual plants being sterile with their
own pollen. I have actually got on my list Eschscholtzia (673/3. See
"Animals and Plants," II., Edition II., page 118.) for fertilising with
its own pollen, though I did not suspect it would prove sterile, and
I will try next summer. My object is to compare the rate of growth of
plants raised from seed fertilised by pollen from the same flower and by
pollen from a distinct plant, and I think from what I have seen I shall
arrive at interesting results. Dr. Hildebrand has lately described
a curious case of Corydalis cava which is quite sterile with its own
pollen, but fertile with pollen of any other individual plant of the
species. (6