I suppose you continue to come together now and then in the evening
. . .Make me a sharer in your new discoveries. Have you finished
your essay on the physiology of plants, and what do you make of
it?. . .

BRAUN TO AGASSIZ.

CARLSRUHE, Whitsuntide, Monday, 1827.

. . .I am in Carlsruhe, and as the package has not gone yet, I add
a note. I have been analyzing and comparing all sorts of plants in
our garden to-day, and I wish you had been with me. On my last
sheet I send some nuts for you to pick, some wholly, some half,
others not at all, cracked. Schimper is lost in the great
impenetrable world of suns, with their planets, moons, and comets;
he soars even into the region of the double stars, the milky way,
and the nebulae.

On a loose sheet come the "nuts to pick." It contains a long list
of mooted questions, a few of which are given here to show the
exchange of thought between Agassiz and his friend, the one
propounding zoological, the other botanical, puzzles. Although most
of the problems were solved long ago, it is not uninteresting to
follow these young minds in their search after the laws of
structure and growth, dimly perceived at first, but becoming
gradually clearer as they go on. The very first questions hint at
the law of Phyllotaxis, then wholly unknown, though now it makes a
part of the most elementary instruction in botany.* (* Botany owes
to Alexander Braun and Karl Schimper the discovery of this law, by
which leaves, however crowded, are so arranged around the stem as