From Fritz Müller 2 August 1866
August. 2. 66.
My Dear Sir,
Your kind letter of May 23d arrived here only July 24th.—1 In the meantime I could observe but a few specimens of one of our species of Oxalis; the length of the styli is very variable even in the flowers of the same plant, but whether the species is really trimorphic, I am not yet able to say.2
In my last letter I gave you a short account of an Orchid having three fertile stamens.3 The species is not very rare and I have already seen numerous ears, all the flowers of which showed the same number of fertile stamens. In a closely allied species from Bahia,4 which I saw in the garden of a Frenchman, I was much surprised at finding but one fertile stamen as in other plants of the tribe. It is curious, that the number of fertile stamens while it furnishes an excellent character for dividing the Orchids into two main groups, in this case is not even of generic value.5
Have you ever seen the flowers of Notylia?6 The stigma forms a very narrow slit, to which I found it impossible to cause the pollinia to adhere; at the same time the ovula have a very rudimentary appearance. Thus for some time I supposed the plant to be a male one, but afterwards I met with seed-capsules, the columna of which had evidently borne an anthera, while the stigma seemed to have been of the same form as in the supposed male flowers. Besides I convinced myself that in some other Orchids the ovula are in a very rudimentary estate at the time when the flower is expanded and that only some weeks afterwards they become ready for impregnation. This is, for instance, the case with two self-fertilizing species of the tribe of Epidendreae; (one of them belongs to the genus Isochilus).— Of these species I can send you some drawings if you shd desire it.—7
The fine Orchid, of which I send you a drawing, seemed to me to be interesting by the two stigmas being widely separated and situated at the inside of leaf-like processes projecting beyond the anther.—8
In your paper on the dimorphism of Linum you say that it had occurred to you, that possibly a species might be dimorphic in function, though not in structure.9 Some observations, which I casually made, seem to confirm this view and to prove that some species are completely barren or nearly so with pollen of the same individual plant. Thus I saw a large plant of an Octomeria; it had more than eighty monophyllous stalks,10 each with about a dozen yellow flowers; on most of the stigmas which I examined I found numerous (6–12) pollinia; but this plant yielded only two seed-capsules. Afterwards I have seen other plants, apparently of the same species, with numerous seed-capsules. I must add, that in the neighbourhood of the first plant I could not detect any other plant of the same species.— A very large plant of a Serjania, widely spreading over a hedge, and as far as I know, about a mile distant from the next plant of the same species, (the same, from which the fig. 20 of my paper on the wood of climbing plants11 was taken) was covered for many weeks by thousands of flowers, which were visited all the day long by numberless insects, (—humble-bees, beetles, butterflies, etc.—); but only very few seed-capsules were produced in the last weeks and I suppose, from their appearance, that none of these capsules, (as yet unripe), will give good seed.— Last year I had raised some plants of Eschscholtzia californica; one of them began to flower about a month before the others, and in this time it yielded not even a single seed-capsule; but no sooner had a neighbouring plant expanded its first flowers, than germens12 of the former plant began to swell; the second plant was fertile from the beginning.—
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Seeds use to fall to the ground, as soon as the seed-capsules open and in this case they are commonly dark-coloured;13 if on the contrary, they remain attached to the open valvæ,14 in all the cases, I know, either the seeds themselves, or the arillus, or the interior of the valvæ are brightly coloured so as to attract the attention,15 which may carry the seeds to distant places. Thus the large valvæ of a Tabernaemontana are filled with a bright red pulpa;—the black and shining seeds of a Paullinia are half-imbedded into a white arillus and fixed to red valvæ,—and the seeds of a fine small tree related to Acacia or Inga, which also for some time remain attached to the valvæ, are black and white and visible at a great distance.—
〈half a page excised〉 hundred miles beyond the actual sea-coast was once covered by a huge glacier!—?—16
I am very glad to hear that Nägeli and my old friend Oscar Schmidt are with us.—17 My brother, Dr. Hermann Müller of Lippstadt, (Prussia) who is thoroughly conversant with the natural history of mosses, is collecting the facts bearing on the change of species, which these plants may offer.—18
Wishing that this letter may find you in good health, believe me, dear Sir, with sincere respect very truly yours
Gives some observations on orchids and on some plants which seem to be dichogamous.
Please cite as
Darwin Correspondence Project, “Letter no. 5173,” accessed on 22 February 2017, http://www.darwinproject.ac.uk/DCP-LETT-5173