152 THE STORY OF THE PLANTS. 



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 dispersed. In the 

 mouse-ear chickweed the capsule 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 hap- 

 pens 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 fre- 

 quently happens that the fruit does not open, as 

 in the oak or the elm; and- when there is only one 

 seed, the fruit and seed become almost indistin- 

 guishable, and are popularly regarded as a seed 

 only. For example, in the pea, we distinguish at 

 once between the pod, which is a fruit containing 

 many seeds, and the pea which is one such seed 

 among the many; but in wheat or oats the fruit 

 is small and one-seeded, and its covering is so 

 closely united with the seed as to be practically 

 inseparable. Fruits like these do not open, and 

 are dispersed whole. . The fruits of most compos- 

 ites are crowned by the feather-like hairs which 

 represent the calyx, and float on the breeze as 

 thistledown or dandelion clocks (Figs. -42, 43, 44, 

 45). John-go-to-bed-at-noon, an English compos- 



