... I am making slow progress with the Asters. The original types of all the older species I shall certainly make out; but the limitation of the species presents great, if not insuperable difficulties. I have read nearly all of Darwin’s “Power of Movement in Plants.” It is a veritable research, with the details all recorded; and so it is dull reading. I think it will give the impression to most readers that the terms “geotropism,” “epinasty,” is “hyponasty,” etc., contain more of explanation than in fact they do. Yet now and then a remark should prevent this, as on page 569, and notably on page 545, at the close of the chapter, intimating,--I suppose with reason--that the term “gravity” or “gravitation” is quite misapplied. I have just taken up Wallace’s “Island Life,” and find the earlier chapters most clear and excellent, but without novelty. The idea of the persistence of continents is most commonplace in America since Dana’s address in (I think) 1845, and I should have thought Wallace would have known of the entire prevalence of that view, at least in the western world. Rely on me, dear De Candolle, to keep you _au courant_ with all that concerns your friends here, among which always remember your devoted, ASA GRAY. TO GEORGE ENGELMANN. KEW, February 19, 1881. MY DEAR ENGELMANN,--A few days, or say a week ago, we were gratified by receiving your pleasant letter of the 31st January. I hasten to reply before we get afloat again, when writing becomes precarious. Just now Mrs. Gray and I have our evenings together in our quiet lodgings, that is, whenever we are not dining out or the like, which is pretty often. You know of our movements, then, up to our return here. The Spanish trip was very pleasant and successful, and the three weeks afterward in Paris both useful and enjoyable. As to botany, it was all given to Aster and Solidago, at the Jardin des Plantes, and at Cosson’s, who has the herbarium of Schultz,[116] Bip., which abounds with pickings from many an herbarium.