From Asa Gray [27 and 29 August] and 2 September 1
to carry down the pollinia, taken from one flower on the point of a fine needle, to the stigma of another flower, have failed,—the pollinia lodging above the stigma or over on the dorsal face.2 I enclose a spike of S. cernua.
Sept. 2d. That Drosera filiformis should show no sensitiveness is perhaps not remarkable, for it is not well arranged for fly-catching.3 But I have got some D. rotundifolia, & tried it with atoms of fresh fish laid on the viscid tips, but I could detect no movement either immediate or later. Yet I could see that some of the leaves had their bristles turned inwards and had been catching flies. I have been to-day into the country and have brought in some fres〈h〉 D. rotundifolia, to try again to-morrow.
The most marked diœcio-dimorphous flowers I know are in Rubiaceæ, and the most familiar cases are in Houstonia (Oldenlandia, but the old name & genus will be restored) specially our H. purpurea and the everywhere common H. cærulea, and Mitchella repens. Spermacoce virginiana & Diodia teres, also show it. I have no data for a list; but the cases are numerous. I will make any observations you will indicate next spring.4
What you say of Mill well accords with what Prof. Henry of Smithsonian Instn. says of your investigations., your method, &c,—and he is the best judge of the logic of investigation I know of.5
Gives some observations on the sensitivity of Drosera species and comments on cases of "dioecio-dimorphism".
Please cite as
Darwin Correspondence Project, “Letter no. 3242,” accessed on 23 January 2017, http://www.darwinproject.ac.uk/DCP-LETT-3242