the Developement of the seminal Germ. C 258 
.ought to rise above ground in obedience to the stimulus of air, 
which all cotyledons do not; and all seeds ought to germinate, if 
not in the water, at least in the earth, though many of them will 
germinate in neither; but on trunks and stumps of trees, as many 
of the Mosses; or on the bare and flinty rock, as many of the 
Lichens. And if the radicle is naturally stimulated by moisture, 
and the cotyledons and plumelet by air, and each elongated in 
the direction of its exciter; then, if an inverted seed is so placed 
by art that moisture shall reach it only from above, and air only 
from below, the radicle ought unquestionably to elongate itself 
by ascent, because that is the direction of its exciter; and the 
plumelet ought also to elongate itself by descent, because that is 
the direction of its exciter. But this did not happen in the case 
of any of Du Hamel's inversions, in one or other of which the sup- 
posed conditions must have been almost literally fulfilled ; nor 
did it happen in the case of the following experiment, which was 
instituted expressly for the purpose of putting Dr. Darwin's hypo- 
thesis to the test. = ^. | 
On the 24th of July 1812 I procured a tube of glass of four 
inches in length, and nearly an inch in diameter, which I filled 
with garden mould, and suspended from the ceiling of my study. 
Into the lower extremity of the tube I then introduced a kidney- 
bean and a grain of wheat, inserting them in the mould by some- 
what more than the one-half, with the apex of the radicle up- 
wards, and the base of the seed touching the inner surface of the 
tube, that the process of germination might be readily traced 
through the glass. The earth was then almost wholly above 
them; and the water with which it was occasionally moistened 
was applied at the upper extremity, so as to come to the seeds 
from above, as well as in small quantities at a time, so as just to 
wet the mould sufficiently, but not to ooze out at the lower ex- 
tremity. 
