WHAT PLANTS DO FOR THEIR YOUNG. 165 



a one-seeded nut, with its edge produced into 

 a leathery or papery wing, which serves to 

 float it. 



But more often the fruit at maturity opens 

 and scatters its seeds, as we see in the pea, the 

 wild hyacinth, and the iris. Sometimes the 

 seeds so released merely drop upon the ground, 

 but most often some device exists for scattering 

 them to a distance, so as to obtain the advantage 

 of unexhausted soil for the young seedling. Thus 

 most capsules open at the top, so that the seeds 

 can only drop out when the wind is high enough 

 to carry them to some distance. In the poppy- 

 head the capsule opens by pores at the side, 

 and, if you shake one as it grows, you will find 

 it takes a considerable shaking to dislodge the 

 seeds from the walls of their chamber. Thus 

 only in high winds are the poppy seeds dis- 

 persed. In the mouse -ear chickweed the cap- 

 sule is directed slightly upward at the end for 

 a similar purpose. Sometimes, again, the valves 

 of the fruit open elastically and shoot out the 

 seeds; this device is familiarly known in the 

 garden balsam, and it occurs also in the little 

 English wallcress. The sandbox- tree of the 

 West Indies has a large round woody capsule, 

 which bursts with a report like a pistol, and 

 scatters its seeds with such violence as to inflict 

 a severe wound upon anybody who happens to 

 be struck by them. 



Where seeds are numerous, they are oftenest 

 dispersed in some such manner, by the capsule 

 opening naturally and scattering its contents ; 

 but where they are few in number, it more 



