LIST OF PLATES ix 



Facing page 

 Plate IX. Flower-clusters of dogwood (Cornua florida), showing a 

 highly developed and conspicuous involucre, probably attractive 



to pollinating insects . 172 



Plate X. Thistle fruits, adapted for dispersal by the wind . .192 



Plate XI. Tree ferns in Ceylon 282 



Plate XII. Improvement of corn. The upper picture shows the 

 effect of drying seed corn by artificial heat. The rows near 

 the middle grew from kiln-dried seed, the others from ordinary 

 seed. The lower picture shows the effect of cross-pollination 

 and of self-pollination on the growth of corn from the seed. 

 The two rows of spindling plants at the left grew from seed pro- 

 duced by self-pollination, the larger plants of the other rows 

 from seed produced by cross-pollination . . 314 



Plate XIII. Fruiting banana plants. The natural slitting of the 

 leaves by the wind serves to prevent them from being blown 

 away bodily during tropical storms ...... 328 



Plate XIV. Oak saplings springing from a stump. Oak, chestnut, 

 and many other hard-wood trees are most quickly replaced on 

 cut-over woodlands by allowing young trees to grow from the 

 stumps 352 



