260 : . The Rev. Parnick KEITH bit 
times, and regarded as affording a rational solution of the curious 
problem that forms the subject of the present Paper*. ‘To argu- 
ments, therefore, conflicting with such high authorities, it may 
well be supposed that I do: not solicit the notice of this learned. 
and enlightened Society but with fear and trembling. 
But the grand defect of Mr. Knight's hypothesis is, that it does. 
not at all account for the ascent of the plumelet, unless my recol- 
lection of his Paper on this subject is itself defective. And in- 
deed the ascent of the plumelet upon Mr. Knights. principles. 
seems to me to be next to impossible, though itis made to ascend. 
notwithstanding. For if the principle of gravitation is found to 
act so very powerfully upon the radicle, should it not be found to. 
act also in a similar manner upon the plumelet, and to prevent 
its ascent altogether ? which, if it is not so heavy as the radicle, 
is at least specifically heavier than atmospheric air, and ought 
eonsequently to be subject to the influence of gravitation. We 
cannot, therefore, regard the power of gravitation as being the 
cause of the radicle’s descent, unless we are at the same time 
shown how it comes to exert no influence upon the plumelet. 
Much less are we to regard it in that light, if it can be shown, on 
the contrary, that there are cases in which the radicle is developed 
in a direction totally opposite to that of the force of gravitation, 
that is, by ascent, as may be exemplified in the germination of 
the seed of the misseltoe. 
The seeds of this plant germinate, as: is well known; not in the 
ground, but on branches of the oak or apple-tree ; or it may be 
of some other tree, where they are accidentally left by birds. 
They will also germinate even when made to adhere to a branch 
by means of human aid}, which, from their glutinous nature; 
they may readily be made to do, though I have not myself been 
* Lectures on Agric. Chem. p. 30, + With. Arrang. ii. 203. 
able 
