338 THE WORLD OF LIFE 



seed-boxes are often very hard, as in the hazel-nut, or intensely 

 so_, as in the Brazil-nut and many other tropical species. 



But, on further consideration, 1 believe that this apparently 

 obvious conclusion is not correct; and that nuts are, as a rule, 

 intended to be eaten. I am not aware that this question has 

 yet been discussed by botanists, and as it is one of much inter- 

 est and exhibits one of the curious and indirect ways in which 

 nature works for the preservation of species, both in the vege- 

 table and animal world, I will briefly explain my views. 



The first point for our consideration is, that most nuts are 

 edible to some animals, and a large number are favourite foods 

 even to ourselves. Then they are all produced on large trees 

 or shrubs of considerable longevity, and the fruits (nuts, 

 acorns, etc.) are produced in enormous quantities. If now 

 we consider that in all countries which are undisturbed by 

 man, the balance between forest and open country, and be- 

 tween one species and another, only changes very slowly as 

 the country becomes modified by geographical or cosmical 

 causes, we recognise that, as in the case of animals, the number 

 of individuals of each species is approximately constant, and 

 there is, broadly speaking, no room for another plant of any 

 particular kind till a parent plant dies or is destroyed by fire 

 or tempest. Imagine then the superfluity of production of 

 seed in an oak, a beech, or a chestnut forest; or in the nut- 

 groves that form their undergrowth in favourable situations. 

 Countless millions of seeds are produced annually, and it is 

 only at long intervals of time, when any of the various causes 

 above referred to have left a space unoccupied, that a few 

 seeds germinate, and the best fitted survives to grow into a 

 tree which may replace its predecessor. 



But when every year ten thousand millions of seeds fall 

 and cannot produce a tree that comes to maturity, any cause 

 which favoured their wider dispersal would be advantageous, 

 even though accompanied by very great destruction of seeds, 

 and such a cause is found when they serve as food to herbiv- 

 orous mammals. For most of these go in herds, such as swine, 



