To Francis Darwin   12 September [1878]¹

My dear F.

I have been very glad to hear how you are getting on. It really seems that you must trust to your own observations alone on stomata.² May not the stomata be variable even in the same species. Such variation may be expected in all characters which differ much in allied species of the same genus;³ & if I remember right the stomata do differ in the species of the same genus.— It certainly looks as if Sachs’ view was largely right,⁴ (surely some of your former cases were opposed to his view) but I cannot understand the length of time which Mer found that leaves could exist in water, especially with Ivy.⁵ How are stomata in Ivy?— I found also that leaves of Mimosa & Trifolium resupinatum lived long submerged.—⁶ I think that you will come to some interesting results.—

Yesterday I made a little observation which interested me: I put Drosera under the compound microscope, fastening back of old leaf with shell-lac to stick, & a tentacle did not circumnutate in the least during 7$\frac{1}{2}$ hours.; nor was it in the least heliotropic. I then touched secretion with atom of raw meat, not leaving any meat on gland, & in 23 seconds tentacle began to curve!⁷ I think we have observed enough to affirm that growth is always accompanied by circumnutation, & as the tentacle though so sensitive to animal matter did not circumnutate we may conclude that it was not growing; so Batalin must be wrong that the movement is partly due to growth.⁸

We see, also, how different such movements are to growth movements.— I wish you w^d. make a note & enquire whether any Barbery bush in a pot is in flower in Kew; for I sh^d like to secure old flower to stick, & observe whether the sensitive stamens circumnutate.⁹ Lotus Jacobæus, I have just thought will be good to observe about pulvinus; for the cotyledon for first 4 or 5 days do not go to sleep, but do afterwards.¹⁰ Is pulvinus developed at first?

We are all well & fairly jolly, & all the jollier as Snow¹¹ has gone.— Bernard¹² is as sweet as sugar, but very contradictory. It grew wonderfully dark about half an hour ago; so I said “how dark it is”; so he shouted out “oh no”.— I then added I think it will soon rain, & he again shouted out “oh dear no” “oh dear no”.

I suppose the glass tubes will come tomorrow; but I won’t use them till your return.¹³

GoodBye dear old fellow | C. Darwin