LINNEAN 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, accordingly, 

 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 Pterocarya is, on the contrary, very hard and 

 stony, and even the interior portion — the walls and pillars sur- 

 rounding 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 Juglans, on the contrary, the lobes are so much 

 larger, that it rather seems as if the fruit sent projections into the 

 seed. That the present 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 sub- 

 terranean 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 oblauceolate outline. I do not know of any attempt to explain 

 this peculiar form. That which I would suggest is as follows : — 

 The leaves of the Evergreen Oak are 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 they 



