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V. On the Direction of the Radicle and Germen during the 
Vegetation of Seeds. By Thomas Andrew Knight, Esq. 
F. R. S. In a Letter to the Right Hon. Sir Joseph Banks, 
K.B. P.R.S. 
Read January 9, 1806. 
MY DEAR SIR, 
It can scarcely have escaped the notice of the most inatten- 
tive observer of vegetation, that in whatever position a seed is 
placed to germinate, its radicle invariably makes an effort to 
descend towards the centre of the earth, whilst the elongated 
germen takes a precisely opposite direction ; and it has been 
proved by Du Hamel* that if a seed, during its germination, 
be frequently inverted, the points both of the radicle and 
germen will return to the first direction. Some naturalists 
have supposed these opposite effects to be produced by gra- 
vitation ; and it is not difficult to conceive that the same agent, 
by operating on bodies so differently organized as the radicle 
and germen of plants are, may occasion the one to descend 
and the other to ascend. 
The hypothesis of these naturalists does not, however, appear 
to have been much strengthed by any facts they were able 
to adduce in support of it, nor much weakened by the argu- 
ments of their opponents ; and therefore, as the phenomena 
* Physique des Arbres, 
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