Of the Developement of the seminal Germ. 253 
and the latter will in like manner bend itself up till it reaches the 
air. And no human art has ever been able to make them assume 
contrary directions, or to convert the one into the other, as the root 
and branches of the vegetating plant may afterwards be some- 
times converted. 
Du Hamel, whom no phytologist has ever surpassed in the in- 
vention of expedients to unmask or to control the operations of 
the vegetative principle, instituted a variety of experiments with 
a view to effect this conversion, and failed in them all. He first 
placed an acorn between two wet sponges suspended from the 
ceiling of his room, so as that the radicle was uppermost and the 
plumelet undermost. ‘The result however was, that the radicle, 
after bursting its integuments, assumed a downward direction, 
and the plumelet in its turn an upward direction, till each had 
gained its natural position. He then filled a tube with earth, 
and planted also an acorn in it in an inverted position. But the 
radicle and plumelet had no sooner escaped from their envelopes, 
than they began to assume their natural direction as before. He 
then filled another tube with earth, of a diameter so small, that 
an acorn when introduced into it touched the internal surface on 
all sides. It was planted in its natural position, and allowed to 
remain so till the radicle appeared. ‘The tube was then inverted, 
and the radicle began immediately to bend itself downwards. 
The tube was again ironies and the radicle resumed its original 
direction *, | | 
Such is the ec EEE of the radicle to fix itself i in 
the soil, and of the plumelet to escape into the air. How is this 
tendency to be accounted for? A great many conjectures have 
been offered in reply to the inquiry, without having done much 
to elucidate the subject. Some have attributed the phenomenon 
* Physique des Arbres, tome ii, chap. 6. 
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