262 ‘The Rev. Patrick KEITH on | 
intro-susception of particles deposited throughout the whole of 
its extent. If, therefore, we regard the additions deposited at the 
point of the radicle, as being originally almost fluid, which they 
must indeed be, we shall then find in that fluidity a cause appa- 
rently adequate to the effect ; the part deposited being thus im- 
mediately subject to the law of gravitation, and incapable of sup- 
porting itself in a vertical position, even though placed in the soil. 
And in like manner the mode of augmentation displayed by the 
plumelet or stem seems calculated rather to facilitate the ascend- 
ing direction, which it actually assumes from the support that is | 
thus gradually distributed throughout the whole of its extent. 
And hence a sort of plausibility is given to the hypothesis. | 
But after all it will not bear the test of a rigid scrutiny; for it 
will not account for the ascent of the radicle in the case of the 
misseltoe, because the force of gravitation is here counteracted ; 
nor for the re-assumption of a vertical position by the plumelet 
that has been inverted, because its mode of growth seems favour- 
able to elongation only in a straight line ; nor for the phenome- 
non of the pendent stem, asin the case of Cactus flabelliformis and 
others ; because, upon the very principle -— its growth 
ought to have been upright. T 
The radicle does not therefore descend by virtue of thà law of 
gravitation, nor of the attraction of moisture: but by virtue of an 
energy exerted in the direction of gravitation, and guiding it in- 
fallibly to nourishment and support ; and the plumelet does not 
ascend by virtue of the principle of levity, or of the attraction of 
the air, but by virtue of an energy exerted in opposition to that 
of gravitation, and leading it infallibly to the atmosphere above 
it; so that even in cases of unnatural and inverted experiment 
the energy still acts, and the radicle and plumelet elongate ac- 
cording to the law originally imposed upon them, though it be. 
| even 
