iven by the author.)

Forgive me for scribbling at such unreasonable length; but you are to
blame for having interested me so much.

P.S.--Perhaps you may remember that some two years ago you asked me to
lunch with you, and proposed that I should offer myself again. Whenever
I next come to London, I will do so, and thus have the pleasure of
seeing you.

LETTER 758. TO W. THISELTON-DYER.

(758/1. "The Power of Movement in Plants" was published early in
November, 1880. Sir W. Thiselton-Dyer, in writing to thank Darwin for
a copy of the book, had (November 20th) compared a structure in
the seedling Welwitschia with the "peg" of Cucurbita (see "Power
of Movement," page 102). Dyer wrote: "One peculiar feature in the
germinating embryo is a lateral hypocotyledonary process, which
eventually serves as an absorbent organ, by which the nutriment of the
endosperm is conveyed to the seedling. Such a structure was quite new to
me, and Bower and I were disposed to see in it a representative of
the foot in Selaginella, when I saw the account of Flahault's 'peg.'"
Flahault, it should be explained, was the discoverer of the curious
peg in Cucurbita. Prof. Bower wrote a paper ("On the Germination and
Histology of the seedling of Welwitschia mirabilis" in the "Quart.
Journ. Microscop. Sci." XXI., 1881, page 15.)

Down, November 28th [1880].

Very many thanks for your most kind note, but you think too highly of
our work--not but what this is very pleasant.

I am deeply interested about Welwitschia. When at work on the pegs or
projections I could not imagine how they were first developed, before
they could have been of mere mechanical use. Now it seems possible that
a circle between radicle and hypocotyl may be permeable to fluids, and
thus have given rise to projections so as to expose larger surface.
Could you test Welwitschia with permanganate of potassium: if, like my
pegs, the lower surface would be coloured brown like radicle, and upper
surface left white like hypocotyl. If such an idea as yours, of an
absorbing organ, had ever crossed my mind, I would have tried many
hypocotyls in weak citrate of ammonia, to see if it penetrated on line
of junction more easily than elsewhere. I daresay the projection in
Abronia and Mirabilis may be an absorbent organ. It was very good fun
bothering the seeds of Cucurbita by planting them edgeways, as would
never naturally occur, and then the peg could not act properly. Many of
the Germans