Fruits and Seeds. 2 1 5 



fixed, it is obvious that during the process of 

 untwisting the seed itself would be pressed down- 

 wards, and this mechanism thus serves actually 

 to bury the seed. 



6. If a seed of this plant is laid on the ground, 

 it remains quiet as long as it is dry ; but as soon 

 as it is moistened i.e., as soon as the earth be- 

 comes in a condition to permit growth the outer 

 side of the awn contracts, and the hairs surround- 

 ing the seed commence to move outwards, the 

 result of which is gradually to raise the seed into 

 an upright position with its point on the soil. The 

 awn then commences to unroll, and consequently 

 to lengthen itself upwards, and it is obvious that as 

 it is covered with reversed hairs, it will probably 

 press against some blade of grass or other obstacle, 

 which will prevent its moving up, and will there- 

 fore tend to drive the seed into the ground. If 

 then the air becomes dryer, the awn will again 

 roll up, when from the position of the hairs the 

 feathery awn can easily slip downwards, and will 

 therefore not affect the seed. When moistened 

 once more, it will again force the seed further 

 downwards, and so on until the proper depth is 

 obtained. One of the Mountain Anemones again 

 has essentially the same arrangement, though 

 belonging to a widely separated order. 



7. A still more remarkable instance is afforded by 

 a beautiful South European grass, Stipa pennata 



- 85). The actual seed is small, with a sharp 



