LETTER 683. TO F. MULLER. Down, January 1st, 1874.
No doubt I owe to your kindness two pamphlets received a few days ago, which have interested me in an extraordinary degree. (683/1. This refers to F. Muller's "Bestaubungsversuche an Abutilon-Arten" in the "Jenaische Zeitschr." Volume VII., which are thus referred to by Darwin ("Cross and Self Fert." pages 305-6): "Fritz Muller has shown by his valuable experiments on hybrid Abutilons, that the union of brothers and sisters, parents and children, and of other near relations is highly injurious to the fertility of the offspring." The Termite paper is in the same volume (viz., VII.) of the "Jenaische Zeitschr.") It is quite new to me what you show about the effects of relationship in hybrids—that is to say, as far as direct proof is concerned. I felt hardly any doubt on the subject, from the fact of hybrids becoming more fertile when grown in number in nursery gardens, exactly the reverse of what occurred with Gartner. (683/2. When many hybrids are grown together the pollination by near relatives is minimised.) The paper on Termites is even still more interesting, and the analogy with cleistogene flowers is wonderful. (683/3. On the back of his copy of Muller's paper Darwin wrote: "There exist imperfectly developed male and female Termites, with wings much shorter than those of queen and king, which serve to continue the species if a fully developed king and queen do not after swarming (which no doubt is for an occasional cross) enter {the} nest. Curiously like cleistogamic flowers.") The manner in which you refer to to my chapter on crossing is one of the most elegant compliments which I have ever received.
I have directed to be sent to you Belt's "Nicaragua," which seems to me the best Natural History book of travels ever published. Pray look to what he says about the leaf-carrying ant storing the leaves up in a minced state to generate mycelium, on which he supposes that the larvae feed. Now, could you open the stomachs of these ants and examine the contents, so as to prove or disprove this remarkable hypothesis? (683/4. The hypothesis has been completely confirmed by the researches of Moller, a nephew of F. Muller's: see his "Brasilische Pilzblumen" ("Botan. Mittheilgn. aus den Tropen," hrsg. von A.F.W. Schimper, Heft 7).)
LETTER 684. TO F. MULLER. Down, May 9th, 1877.
I have been particularly glad to receive your letter of March 25th on Pontederia, for I am now printing a small book on heterostyled plants, and on some allied subjects. I feel sure you will not object to my giving a short account of the flowers of the new species which you have sent me. I am the more anxious to do so as a writer in the United States has described a species, and seems to doubt whether it is heterostyled, for he thinks the difference in the length of the pistil depends merely on its growth! In my new book I shall use all the information and specimens which you have sent me with respect to the heterostyled plants, and your published notices.
One chapter will be devoted to cleistogamic species, and I will just notice your new grass case. My son Francis desires me to thank you much for your kindness with respect to the plants which bury their seeds.
I never fail to feel astonished, when I receive one of your letters, at the number of new facts you are continually observing. With respect to the great supposed subterranean animal, may not the belief have arisen from the natives having seen large skeletons embedded in cliffs? I remember finding on the banks of the Parana a skeleton of a Mastodon, and the Gauchos concluded that it was a borrowing animal like the Bizcacha. (684/1. On the supposed existence in Patagonia of a gigantic land-sloth, see "Natural Science," XIII., 1898, page 288, where Ameghino's discovery of the skin of Neomylodon listai was practically first made known, since his privately published pamphlet was not generally seen. The animal was afterwards identified with a Glossotherium, closely allied to Owen's G. Darwini, which has been named Glossotherium listai or Grypotherium domesticum. For a good account of the discoveries see Smith Woodward in "Natural Science," XV., 1899, page 351, where the literature is given.)
LETTER 685. TO F. MULLER. Down, May 14th {1877}.
I wrote to you a few days ago to thank you about Pontederia, and now I am going to ask you to add one more to the many kindnesses which you have done for me. I have made many observations on the waxy secretion on leaves which throw off water (e.g., cabbage, Tropoeolum), and I am now going to continue my observations. Does any sensitive species of Mimosa grow in your neighbourhood? If so, will you observe whether the leaflets keep shut during long-continued warm rain. I find that the leaflets open if they are continuously syringed with water at a temperature of about 19 deg C., but if the water is at a temperature of 33-35 deg C., they keep shut for more than two hours, and probably longer. If the plant is continuously shaken so as to imitate wind the leaflets soon open. How is this with the native plants during a windy day? I find that some other plants—for instance, Desmodium and Cassia—when syringed with water, place their leaves so that the drops fall quickly off; the position assumed differing somewhat from that in the so-called sleep. Would you be so kind as to observe whether any {other} plants place their leaves during rain so as to shoot off the water; and if there are any such I should be very glad of a leaf or two to ascertain whether they are coated with a waxy secretion. (685/1. See Letters 737-41.)
There is another and very different subject, about which I intend to write, and should be very glad of a little information. Are earthworms (Lumbricus) common in S. Brazil (685/2. F. Muller's reply is given in "Vegetable Mould," page 122.), and do they throw up on the surface of the ground numerous castings or vermicular masses such as we so commonly see in Europe? Are such castings found in the forests beneath the dead withered leaves? I am sure I can trust to your kindness to forgive me for asking you so many questions.