THE WORK OF WINDS AND INSECTS 151 



After quite another fashion behave the stamen-flowers. 

 They also take shape out of sight far below, encased in a 

 bladder through which no damp may penetrate. But 

 instead of only one flower, the sac contains many; 

 and when they gain a certain stage, the enclosing sac 

 opens to set them free. Then, in place of growing 

 upward on a long stalk, they break short off and spring 



VALLISNERIA SPIKALIS. 



to the surface, at the time when their pollen is just 

 ripe. 



On first arrival at the surface they are fast shut, 

 and rounded like little globes ; but soon they open, to 

 float as tiny boats on pond or lake. Wonderful little 

 boats, too three flowers joined together forming one 

 boat supported by three outspread sepals, and so 

 constructed as not to overturn even when blown 

 about somewhat roughly. They have power to right 



