PROPAGATION OF THE SPECIES. CHAP. IX. 



dilatation, dependant upon change of weather ; from 

 which, as well as from the additional aid of the fine 

 hairs, which act as so many fulcra, and cling to what- 

 ever object they meet, the seed to which it is attached 

 is kept in continual motion till it either germinates 

 or is destroyed.* 



The awn of Barley, which is beset with a multi- 

 tude of little teeth all pointing to its upper ex- 

 tremity, presents also similar phenomena. For when 

 the seed with its awn falls from the ear and lies flat 

 upon the ground, it is necessarily extended in its 

 dimensions by the moisture of the night, and con- 

 tracted by the drought of the day. But as the teeth 

 prevent it from receding in the direction of the 

 point, it is consequently made to advance in the 

 direction of the base of the seed, which is thus often 

 carried to the distance of many feet from the stalk 

 on which it grew. If any one is yet sceptical with 

 regard to the travelling capacity of the awn, let him 

 only introduce an awn of Barley with the seed upper- 

 most between his coat and shirt sleeve at the wrist, 

 when he walks out in the morning, and by the time 

 he returns to breakfast, if he has walked to any 

 great distance he will find it up at his arm-pit. This 

 journey has been effected by means of the continued 

 motion of the arm, and consequently of the teeth of 

 the awn acting as feet to carry it forward. 



It is obvious, however, that the modes of dis- 

 persion now stated can never carry the seed to any 



* Withering Arrang. vol. ii. p. 6lO. 



