Discusses whether or not "male" Acropera bear fruit. JS's interpretation of Acropera pollination is ingenious. Pollen-tubes of some cleistogamous flowers germinate in the anthers.
Down. | Bromley. | Kent. S.E.
I thank you most sincerely for your kindness in writing to me, & for very interesting letter. Your fact has surprised me greatly, & has alarmed me not a little, for if I am in error about Acropera I may be in error about Catasetum. Yet when I call to mind the state of the placentæ in A. luteola, I am astonished that they should produce ovules. You will see in my book that I state that I did not look at the ovarium of A. Loddegesii. Would you have the kindness to send me word, which end of the ovarium is meant by apex (that nearest the flower?) for I must try & get this species from Kew & look at its ovarium.
I shall be extremely curious to hear whether the fruit, which is now maturing, produces a large number of good & plump seed; perhaps you may have seen the ripe capsules of other Vandeæ & may be able to form some conjecture what it ought to produce. In the young unfertilised ovaria of many Vandeæ, there seemed an infinitude of ovules. In desperation it occurs to me as just possible, as almost every thing in nature goes by gradation, that a properly male flower might occasionally produce a few seeds, in same manner as female plants sometimes produce a little pollen. All your remarks seem to me excellent & very interesting & I again thank you for your kindness in writing to me.
I am pleased to observe that my description of the structure of Acropera seems to agree pretty well with what you have observed. Does it not strike you as very difficult to understand how insects remove the pollinia & carry them to the stigmas?— Your suggestion that the mouth of the stigmatic cavity may become charged with viscid matter & thus secure the pollinia, & that the pollen-tubes may then protrude, seems very ingenious & new to me; but it would be very anomalous in Orchids, i.e. as far as I have seen. No doubt, however, though I tried my best, that I shall be proved wrong in many points. Botany is a new subject to me.—
With respect to the protrusion of pollen-tubes, you might like to hear (if you do not already know the fact) that, as I saw this summer, in the little imperfect flowers of Viola & Oxalis, which never open, that the pollen-tubes always come out of the pollen-grain, whilst still in the anthers, & direct themselves in a beautiful manner to the stigma seated at some little distance.—
I hope that you will continue your very interesting observations, & I beg leave to remain | Dear Sir | Yours faithfully & obliged | Charles Darwin
- f1 3805.f1The year is established by the relationship to the letter from John Scott, 11 November 1862.
- f2 3805.f2Letter from John Scott, 11 November 1862.
- f3 3805.f3See letter from John Scott, 11 November 1862 and nn. 2, 3, and 7.
- f4 3805.f4Orchids, p. 210.
- f5 3805.f5CD's notes on his observations of Viola canina and Oxalis acetosella, made in May and June 1862, are preserved in DAR 111: 3--5, 44. See also letter to J. D. Hooker, 30 May , letter to W. E. Darwin, [31 May 1862], and letter to Asa Gray, 10--20 June .