JUGLANDE^E 513 



In Pterocarya, on the contrary, the fruits are much smaller, 

 and wings therefore more suitable. Possessing in themselves 

 the means of dispersal, they have no need of offering any 

 attraction 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 the 

 weather, and from the attacks of most insects &c., which would 

 not help in their dispersal, it offers no obstacle to larger animals. 

 That of Pterocarya, on the contrary, is very hard and strong, 

 and even the interior portion (the walls and pillars surrounding 

 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 pericarp ; in Juglans, 

 on the contrary, the lobes are so much larger that it rather 

 seems as if the pericarp 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 the Oak and many other 

 plants with subterranean cotyledons. 



These scales evidently indicate the former presence of actual 

 leaves which are now no longer required. The curious lobings 

 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 function, except as a 

 storehouse of nourishment for the seedling. 



Seedlings. Two very distinct types of seedlings may be 

 noted in the Order, namely, those with subterranean cotyle- 

 dons and those with aerial ones. The former are represented 

 by Juglans regia (fig. 661). The hypocotyl is undeveloped, and 

 the cotyledons remain enclosed in the bony endocarp during 

 germination ; they develop petioles sufficiently long to en- 

 able the plumule to make its exit from the apex of the nut 

 and grow upwards. The internodes of the stem between the 

 aborted leaves noted in the seed attain a considerable length 

 during germination. Four or five pairs of these scales occur 

 before a perfect leaf is developed. The first perfect form 



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