My dear Sir

I have been particularly glad to receive your letter of March 25^th. on Pontederia, for I am now printing a small book on Heterostyled plants & on some allied subjects.¹ I feel sure that 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 U. States has described a species & seems to doubt whether it is Heterostyled; for he thinks the difference in the length of the pistil depends merely on its growth!—² In my new book I shall use all the information & specimens which you have sent me with respect to other heterostyled plants, & your published notices.³

One chapter will be devoted to Cleistogamic species, & I will just notice your new grass case.—⁴ My son Francis desires me to thank you much for your kindness with respect to the plants which bury their seeds.⁵

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, & the Gauchos concluded that it was a burrowing animal like the Bizcacha.⁶

With all good wishes & thanks, | Yours very sincerely | Ch. Darwin