Volume II Part 53 (1/2)
A letter to Dr. Asa Gray (September 5th, 1857) gives the substance of the paper in the ”Gardeners' Chronicle”:--
”Lately I was led to examine buds of kidney bean with the pollen shed; but I was led to believe that the pollen could HARDLY get on the stigma by wind or otherwise, except by bees visiting [the flower] and moving the wing petals: hence I included a small bunch of flowers in two bottles in every way treated the same: the flowers in one I daily just momentarily moved, as if by a bee; these set three fine pods, the other NOT ONE. Of course this little experiment must be tried again, and this year in England it is too late, as the flowers seem now seldom to set.
If bees are necessary to this flower's self-fertilisation, bees must almost cross them, as their dusted right-side of head and right legs constantly touch the stigma.
”I have, also, lately been re-observing daily Lobelia fulgens--this in my garden is never visited by insects, and never sets seeds, without pollen be put on the stigma (whereas the small blue Lobelia is visited by bees and does set seed); I mention this because there are such beautiful contrivances to prevent the stigma ever getting its own pollen; which seems only explicable on the doctrine of the advantage of crosses.”
The paper was supplemented by a second in 1858. (”Gardeners' Chronicle”, 1858, page 828. In 1861 another paper on Fertilisation appeared in the ”Gardeners' Chronicle”, page 552, in which he explained the action of insects on Vinca major. He was attracted to the periwinkle by the fact that it is not visited by insects and never set seeds.) The chief object of these publications seems to have been to obtain information as to the possibility of growing varieties of leguminous plants near each other, and yet keeping them true. It is curious that the Papilionaceae should not only have been the first flowers which attracted his attention by their obvious adaptation to the visits of insects, but should also have const.i.tuted one of his sorest puzzles. The common pea and the sweet pea gave him much difficulty, because, although they are as obviously fitted for insect-visits as the rest of the order, yet their varieties keep true. The fact is that neither of these plants being indigenous, they are not perfectly adapted for fertilisation by British insects. He could not, at this stage of his observations, know that the co-ordination between a flower and the particular insect which fertilises it may be as delicate as that between a lock and its key, so that this explanation was not likely to occur to him. (He was of course alive to variety in the habits of insects. He published a short note in the ”Entomologists Weekly Intelligencer”, 1860, asking whether the Tineina and other small moths suck flowers.)
Besides observing the Leguminosae, he had already begun, as shown in the foregoing extracts, to attend to the structure of other flowers in relation to insects. At the beginning of 1860 he worked at Leschenaultia (He published a short paper on the manner of fertilisation of this flower, in the ”Gardeners' Chronicle”, 1871, page 1166.), which at first puzzled him, but was ultimately made out. A pa.s.sage in a letter chiefly relating to Leschenaultia seems to show that it was only in the spring of 1860 that he began widely to apply his knowledge to the relation of insects to other flowers. This is somewhat surprising, when we remember that he had read Sprengel many years before. He wrote (May 14):--
”I should look at this curious contrivance as specially related to visits of insects; as I begin to think is almost universally the case.”
Even in July 1862 he wrote to Dr. Asa Gray:--
”There is no end to the adaptations. Ought not these cases to make one very cautious when one doubts about the use of all parts? I fully believe that the structure of all irregular flowers is governed in relation to insects. Insects are the Lords of the floral (to quote the witty ”Athenaeum”) world.”
He was probably attracted to the study of Orchids by the fact that several kinds are common near Down. The letters of 1860 show that these plants occupied a good deal of his attention; and in 1861 he gave part of the summer and all the autumn to the subject. He evidently considered himself idle for wasting time on Orchids, which ought to have been given to 'Variation under Domestication.' Thus he wrote:--
”There is to me incomparably more interest in observing than in writing; but I feel quite guilty in trespa.s.sing on these subjects, and not sticking to varieties of the confounded c.o.c.ks, hens and ducks. I hear that Lyell is savage at me. I shall never resist Linum next summer.”
It was in the summer of 1860 that he made out one of the most striking and familiar facts in the book, namely, the manner in which the pollen ma.s.ses in Orchis are adapted for removal by insects. He wrote to Sir J.D. Hooker July 12:--
”I have been examining Orchis pyramidalis, and it almost equals, perhaps even beats, your Listera case; the sticky glands are congenitally united into a saddle-shaped organ, which has great power of movement, and seizes hold of a bristle (or proboscis) in an admirable manner, and then another movement takes place in the pollen ma.s.ses, by which they are beautifully adapted to leave pollen on the two LATERAL stigmatic surfaces. I never saw anything so beautiful.”
In June of the same year he wrote:--
”You speak of adaptation being rarely VISIBLE, though present in plants.
I have just recently been looking at the common Orchis, and I declare I think its adaptations in every part of the flower quite as beautiful and plain, or even more beautiful than in the Woodp.e.c.k.e.r. I have written and sent a notice for the ”Gardeners' Chronicle” (June 9, 1860. This seems to have attracted some attention, especially among entomologists, as it was reprinted in the ”Entomologists Weekly Intelligencer”, 1860.), on a curious difficulty in the Bee Orchis, and should much like to hear what you think of the case. In this article I have incidentally touched on adaptation to visits of insects; but the contrivance to keep the sticky glands fresh and sticky beats almost everything in nature. I never remember having seen it described, but it must have been, and, as I ought not in my book to give the observation as my own, I should be very glad to know where this beautiful contrivance is described.”
He wrote also to Dr. Gray, June 8, 1860:--
”Talking of adaptation, I have lately been looking at our common orchids, and I dare say the facts are as old and well-known as the hills, but I have been so struck with admiration at the contrivances, that I have sent a notice to the ”Gardeners' Chronicle”. The Ophrys apifera, offers, as you will see, a curious contradiction in structure.”
Besides attending to the fertilisation of the flowers he was already, in 1860, busy with the h.o.m.ologies of the parts, a subject of which he made good use in the Orchid book. He wrote to Sir Joseph Hooker (July):--
”It is a real good joke my discussing h.o.m.ologies of Orchids with you, after examining only three or four genera; and this very fact makes me feel positive I am right! I do not quite understand some of your terms; but sometime I must get you to explain the h.o.m.ologies; for I am intensely interested on the subject, just as at a game of chess.”
This work was valuable from a systematic point of view. In 1880 he wrote to Mr. Bentham:--
”It was very kind in you to write to me about the Orchideae, for it has pleased me to an extreme degree that I could have been of the LEAST use to you about the nature of the parts.”
The pleasure which his early observations on Orchids gave him is shown in such extracts as the following from a letter to Sir J.D. Hooker (July 27, 1861):--
”You cannot conceive how the Orchids have delighted me. They came safe, but box rather smashed; cylindrical old cocoa- or snuff-canister much safer. I enclose postage. As an account of the movement, I shall allude to what I suppose is Oncidium, to make CERTAIN,--is the enclosed flower with crumpled petals this genus? Also I most specially want to know what the enclosed little globular brown Orchid is. I have only seen pollen of a Cattleya on a bee, but surely have you not unintentionally sent me what I wanted most (after Catasetum or Mormodes), viz. one of the Epidendreae?! I PARTICULARLY want (and will presently tell you why) another spike of this little Orchid, with older flowers, some even almost withered.”
His delight in observation is again shown in a letter to Dr. Gray (1863). referring to Cruger's letters from Trinidad, he wrote:--”Happy man, he has actually seen crowds of bees flying round Catasetum, with the pollinia sticking to their backs!”
The following extracts of letters to Sir J.D. Hooker ill.u.s.trate further the interest which his work excited in him:--
”Veitch sent me a grand lot this morning. What wonderful structures!