FRUIT AND SEED OF THE JUGLANDEE. 253 
embryo, with the radicle close to the apex. Gradually, however, 
the cotyledons grow and eventually absorb the whole of the 
endosperm, thus filling the whole of the interior of the seed, 
except, of course, the small portion occupied by the plumule and 
radicle. 
We have seen that in the fruit of Plerocarya four hollow 
spaces gradually form themselves in the originally solid fruit, and 
that into these spaces the seed sends four prolongations, into 
Which again the cotyledons subsequently grow. Now in the 
Walnut a very similar process takes place, only the hollow spaces 
are much larger and confluent with the ovary-cavity, so that 
instead of a solid wall with hollow spaces occupied by the seed, it 
gives the impression as if the seed was thrown into folds occupied 
by the wall of the fruit. To occupy these spaces fully, the 
cotyledons themselves were thrown into folds as we now see 
them. The fruit of Pterocarya is much smaller than that of 
the Horse-chestnut, which doubtless was itself formerly not so 
large as it now is. As it increased, the cotyledons became 
fleshier and fleshier, and found it more and more difficult to 
make their exit from the seed, until at last they have given up 
any attempt to do so. Hence the curious folds, with which we 
are so familiar, are the efforts made by the original leafy cotyle- 
dons to oceupy the interior of the nut. 
Comparison of the Fruits of Pterocarya and Juglans. 
Thus, then, while essentially similar, the fruits of Pterocarya 
and of the Walnut offer several ran kabile differences. They 
resemble in some respects the relations between the fruits of the 
Hornbeam and of the Beech. The fruit of Pterocarya, like 
that of the Hornbeam, is winged, which is not the case with 
the Walnut or the Beech; it is in the two former smaller, 
and a great deal harder than in the two latter. Again, the 
cotyledons of Pterocarya are aerial, while those of Juglans no 
longer 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 large rather than numerous. 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. These seeds form the food of squirrels and other 
animals, which accordingly serve to disperse them, aud thus 
perhaps they are enabled to dispense with any other means of 
LINN. JOURN.—BOTANY, VOL. XXVIII. x 
