274 



STRUCTURE AND VITAL PROCESSES OF PLANTS 



In other cases, the seeds are furnished with aivns, as in many 

 Grasses. Each awn is thickly set with bristles which allow the 

 awn to move only in one direction. As these are, sensitive to 

 moisture, the difference in the amount of moisture in the air 

 lengthens and contracts them, so that the seeds attached to them 

 are slowly hut surely drawn away many inches. 



(h) Dispersed by water. — Many water-plants have seeds 

 or fruits which float. An air-bubble is attached to the seed of 

 the Water-lily which causes it to rise to the surface. The 

 cocoanut is provided with a strong, but light covering, and, if it 

 falls into the sea, it may be carried by the waves hundreds of 

 miles. How many seeds that fall to the ground during the hot 

 season are washed away by the torrents of rain of the bursting 

 monsoon and landed on a spot far away from the mother-plant, 

 the hard seed-shells protecting the tender germ within from 

 destruction! 



{€) Carried by tlie wind.— The winged fruits of so many trees 



are very well known, such 

 as Hopea Wightiana (Kan. 

 Karmara; Afal. llapongu; 

 // ^ Tani. Kongu) or Butea fron- 



dosa, in which the calyx, or 

 the pericarp is enlarged and 



Fif,-. -^72.— Wiiij,'c,l fruit of 

 llopea Wif^litimia. 



Fig. 273. — Winged seed of 

 Stereosperimun. 



becomes a wing in the fruit. In Stereospcrmum {Kan. Puruli; 

 Mai. Patiri; Tarn. Tadiri) the winged appendage belongs to the 

 seed. The fruits of many Composit.T and the seeds of the 

 Asclepiadacea' are provided with silky or feathery hairs (called 

 "pappus" in Compositiu), whirh catch tlic wind and allow the 

 seed to l)e borne away even hy the gentlest breeze. In some 



