XI THE SPECIAL COLOURS OF PLANTS 305 



altogether unattractive, never having any soft, juicy pulp ; 

 while the edible seeds often bear such a small proportion 

 to the hard, dry envelopes or appendages, that few animals 

 would care to eat them. 



The Meaning of Nuts. 



There is, however, another class of fruits or seeds, usually 

 termed nuts, in which there is a large amount of edible matter, 

 often very agreeable to the taste, and especially attractive 

 and nourishing to a large number of animals. But when 

 eaten, the seed is destroyed and the existence of the species 

 endangered. It is evident, therefore, that it is by a kind of 

 accident that these nuts are eatable ; and that they are not 

 intended to be eaten is shown by the special care nature seems 

 to have taken to conceal or to protect them. We see that all 

 our common nuts are green Avhen on the tree, so as not easily 

 to be distinguished from the leaves ; but when ripe they turn 

 l)rown, so that when they fall on to the ground they are equally 

 indistinguishable among the dead leaves and twigs, or on the 

 brown earth. Then they are almost always protected by hard 

 coverings, as in hazel-nuts, which are concealed l^y the enlarged 

 leafy involucre, and in the large tropical brazil-nuts and cocoa- 

 nuts by such a hard and tough case as to be safe from almost 

 every animal. Others have an external bitter rind, as in the 

 walnut; while in the chestnuts and beechnuts two or three 

 fruits are enclosed in a prickly involucre. 



Notwithstanding all these precautions, nuts are largely 

 devoured by mammalia and birds ; but as they are chiefly 

 the product of trees or shrubs of considerable longevity, 

 and are generally i:)roduced in great profusion, the perpetua- 

 tion of the species is not endangered. In some cases the 

 devourers of nuts may aid in their dispersal, as they probably 

 now and then swalloAV the seed whole, or not sufiiciently 

 crushed to prevent germination ; while squirrels have been 

 observed to bury nuts, many of which are forgotten and 

 afterwards grow in places they could not have otherwise 

 reached.^ Nuts, especially the larger kinds which are so 

 well protected by their hard, iiearly globular cases, have their 

 dispersal facilitated by rolling down hill, and more especially 



^ Nature, vol. xv. p, 117. 

 X 



