400 TROPICAL NATURE 



small brown seeds. Others whose seeds are ejected by the 

 bursting open of their capsules, as with the oxalis and many 

 of the caryophyllacese, scrophulariacese, etc., have their seeds 

 very small and rarely or never edible. 



It is to be remarked that most of the plants whose large- 

 seeded nuts cannot be eaten without destroying their germ- 

 inating power as the oaks, beeches, and chestnuts are 

 trees of large size which bear great quantities of fruit, and 

 that they are long lived and have a wide geographical range. 

 They belong to what are called dominant groups, and are 

 thus able to endure having a large proportion of their seeds 

 destroyed with impunity. It is a suggestive fact that they 

 are among the most ancient of known dicotyledonous plants 

 oaks and beeches going back to the Cretaceous period with 

 little change of type, so that it is not improbable that they 

 may be older than any fruit-eating mammal adapted to feed 

 upon their fruits. The attractive coloured fruits on the other 

 hand, having so many special adaptations to dispersal by 

 birds and mammals, are probably of more recent origin. 1 

 The apple and plum tribes are not known earlier than the 

 Miocene period ; and although the record of extinct vegetable 

 life is extremely imperfect, and the real antiquity of these 

 groups is no doubt very much greater, it is not improbable 

 that the comparative antiquity of the fruit-bearing and nut- 

 bearing trees may remain unchanged by further discoveries, 

 as has almost always happened as regards the comparative 

 antiquity of animal groups. 



Attractive Colours of Flowers 



The colours of flowers serve to render them visible and 

 recognisable by insects, which are attracted by secretions of 

 nectar or pollen. During their visits for the purpose of 

 obtaining these products, insects involuntarily carry the 

 pollen of one flower to the stigma of another, and thus effect 

 cross -fertilisation, which, as Mr. Darwin was the first to 

 demonstrate, immensely increases the vigour and fertility of 

 the next generation of plants. This discovery has led to 

 the careful examination of great numbers of flowers, and the 



1 I owe this remark to Mr. Grant Allen, author of Physiological 

 Esthetics. 



