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LIKNEAN SOCIETY OF LONDON. 125
perform the functions of leaves, and never quit the seed. In the
Walnut, as in some other trees, it is an advantage that the seeds
should be more numerous than large. In this way they are able to
contain a supply of nutriment which suffices rapidly to carry the
young plant above the grasses and other low herbage. Such seeds
form the food of squirrels and other animals, which, accordmgly,
serve to disperse them, and thus, perhaps, they are able to dispense
with any other means of transport. Moreover, for such large fruits,
wings would perhaps be scarcely adequate. In Pterocarya, on the
contrary, the fruits are much smaller, and wings are therefore more
suitable. Possessing, then, themselves the means of dispersal,
they have no need of offering any attractions to animals. In fact,
every one which is eaten is so much pure loss. Hence, while the
shell of the Walnut is sufficiently hard to protect the seed from the
severity of weather, and from the attacks of insects, &c., which
would not help in their dispersal, it offers no obstacle to larger
animals. That of Pterocanja is, on the contrary, very hard and
stony, and even the interior portion—the walls and pillars surroundmg
the four hollows—are of the same character, while in the
Walnut they are comparatively quite soft. One reason why the
similarity of construction in the two seeds does not at first strike
the observer is that in Pterocarya the lobes of the seed evidently
enter the fruit ; in Jufflanf!, on the contrary, the lobes are so much
larger, that it rather seems as if the fruit sent projections into the
seed. That the i^resent condition of the Walnut seedling is not
original we have interesting evidence in the presence of small
leaves reduced to minute scales, as in many plants with subterranean
cotyledons. These scales evidently indicate the former
presence of actual leaves, which are no longer required. The
curious lobing and foldings of the seed in the Walnut also remind
us of the time when the cotyledons were variously lobed and
folded, so as to occupy the whole space in the gradually enlarging
seed. At present they seem to fulfil no useful functions.
(2.) " On the shape of the Oak-leaf." In the case of the Oak,
we are so accustomed to the form of its leaf that it does not strike
us as anything peculiar, and comparatively few persons, probably,
ask themselves why it should be as it is. And yet it is peculiar,
unlike that of any of our forest trees, or those of the Evergreen
Oak, so abundant in hotter countries. In botanical phraseology,
the Oak-leaves are deciduous, oblong-lanceolate, or oblong-elliptical,
sinuated with blunt lobes extending not more than half-way down
to the midrib. The sinus between the lobes is generally rounded
off at the bottom. Again, they are rarely symmetrical, the lobes
of the two sides not corresponding. The three points, then, which
give the Oak-leaf its peculiar form are :— (1) the deep, rounded
sinuses; (2) the want of symmetry of the two sides; (3) the oblong
or oblanceolate outline. I do not know of any attempt to explain
tliis peculiar form. That which I would suggest is as follows :
The leaves of the Evergreen Oak arc entire, and small in comparison
with those of the English Oak. During the winter and early spring
they are protected by a series of brown scales, inside which tliey