196 



Fruits and Seeds. 



plants to make its appearance on coral islands, and 

 it is, I believe, the only palm which is common to 

 both hemispheres. 



The seeds of the common Duckweeds (fig. 77) 

 sink to the bottom of the water in autumn, and 

 remain there throughout the winter ; but in the 

 spring they rise up to the surface again and begin 

 to grow. 



9. In a very large number of cases the diffusion 

 of seeds is effected by animals. To this class belong 

 the fruits and berries. In them an outer fleshy 



Fig. 77. LESSER DUCKWEED (Lemna minoi). 



portion becomes pulpy, and generally sweet, enclo- 

 sing the seeds. It is remarkable that such fruits, 

 in order, doubtless, to attract animals, are, like 

 flowers, brightly coloured as, for instance, the 

 Cherry, Currant, Apple, Peach, Plum, Strawberry, 

 Raspberry, and many others. This colour, more- 

 over, is not present in the unripe fruit, but is rapidly 

 developed at maturity. In such cases the actual 

 seed is generally protected by a dense, sometimes 

 almost stony, covering, so that it escapes digestion, 

 while its germination is perhaps hastened by the 



