262 The Rev. Mr. Keith on the [Apnit, 
an objection to Mr. Knight’s hypothesis, the fact of the upward 
growth of the radicle of the misseltoe, at least when the seed is 
lodged on the under side of the supporting branch. But I now 
find that Mr. Knight obviates the objection by saying, that the 
misseltoe has no root, and that the part in question gains the 
bark only by receding from the light, like the stem and tendrils 
of other parasitical plants. 
I am not acquainted with many plants that are strictly parasi- 
‘tical; but I do not find in those with which I am acquainted any 
peculiar disposition to recede from the light. The dodder, 
Cuscuta europea, cannot be said to have it, because it twines 
round a supporting stem from right to left; so that in its very 
outset, it must rather approach the light than recede from it ; 
and again, in every new spire or gyration, broom-rape, Orebanche 
major, does not fiy the light, for it comes up quite erect: and I 
have seen many piants of the misseltoe, Viscum album, whose 
growth is wholly to the south of the point at which they issue 
from the stem, as well as chiefly ascending. Hence if any part 
of the germ of a parasitical seed is found to recede from the 
light, it is most likely, because it is of the nature of a radicle, 
since radicles are known to do so. Besides, the embryo of the 
seed of the missletoe is just like many other embryos, furnished 
with cotyledons, enclosmg a plumelet, and what we are bound 
to call a radicle (though perhaps caulescent), unless for some 
good reason with which I am not yet acquainted ; because it is 
that part of the embryo which first begins to shoot in the process 
of germination, and in a direction opposite to the plumelet. 
In this opinion I am supported by an authority which I am 
sure Mr. Knight will respect, namely, that of the great and 
illustrious Goertner, who expressly describes the embryo of the 
misseltoe as being furnished with a somewhat swollen and capi- 
tate radicle, that is, separated from the cotyledons by a slender 
stipe. All indeed that is situated beneath the cotyledons, may, 
in the opmion of Geertner, be regarded as a radicle in every 
embryo whatever ;* whereas, with regard to the misseltoe, Mr. 
Knight’s opinion implies that all below the cotyledons is a stem. 
But will Mr. Knight allow me to cut off the point of it to see 
whether it will insinuate itself into the bark then? [fitis wholly 
a stem, it ought still todo so. But if it refuses, then it is plain 
that there was something in the point more than a mere stem. 
This experiment must be made and succeed before Mr. Knight 
can establish his position; that is; a graft of the misseltoe must 
succeed by being bound to the outside of the bark of some stock. 
If it be said that it would be unfair to cut off the point because 
it may contain something fitted to make it unite with the 
supporter, then I contend that this something is the very radicle 
m question. 
® De Fruct. et Sem. Introd. 
