270 THE BIOLOGY OF THE SEASONS 



great success with its seeds, and its valuable idiosyncrasy 

 would be handed on, for subtle reasorjs perhaps aug- 

 mented, to an ever-increasing body of descendants. 



Turning now to the many different kinds of fruits, we 

 must, from a general biological point of view, regard the 

 great diversity as an interesting illustration of the variety 

 of solutions that may be offered to one vital problem. 

 Linne recognised five different kinds of fruits, and Lindley 

 thirty-six ; but as this is not a botanical treatise, the smaller 

 number will suffice. First, there are the box-fruits, or 

 capsules, dry in character, and liberating the contained 

 seeds. Poppy-heads and pea-pods at once suggest them- 

 selves as examples. Second, there are splitters, or schizo- 

 carps, also dry, but not liberating the seeds. They break 

 into pieces, each of which encloses a seed. This is true of 

 the fruits of the hemlock and all Umbellifers, of mallows, 

 of Labiates. It is enough to look into the calyx of a ripe 

 White Dead Nettle to see that the fruit has neatly divided 

 into four nutlet-like pieces, each enclosing a single seed. 

 Third, there are nuts and nutlets (achenes), also dry and 

 not liberating the contained seed. In true nuts, such as 

 those of the hazel, there is a very hard fruit-wall, to which 

 the enclosed seed is not adherent ; in the fruits of a butter- 

 cup (achenes) the wall is not hard, and the enclosed seed 

 is not adherent; in grains of wheat the fruit -wall is 

 somewhat leathery, and the envelope of the seed is adherent 

 to it. This may serve as an illustration of how classification 

 proceeds, division within division, as long as there is a 

 clear basis of distinction. 



Turning from the dry to the succulent fruits, we find 

 that there are two main kinds. There are the stone- 

 fruits, or drupes, with three layers, the middle one more or 

 less juicy, and the innermost one (the " stone ") always 

 very hard. Cherries and plums at once suggest them- 



