DIRECT SOWING. 53 



ings on irrigated lands can be made at other seasons. 

 The seed of some Indian species does not keep, and 

 indeed the seed of Sal (Shorea rolusta) often germinates 

 before it falls, and must therefore be sown as soon as it 

 ripens. In those regions of the Himalayas, where 

 snow may lie until late in the spring, both autumn and 

 spring sowings are made, there being perhaps no 

 decided balance in favour of the one or the other season. 



c. Covering the Seed. 



The objects of covering the seed are chiefly the 

 following : 



(1.) To protect it against sudden changes of moisture 



and temperature. 

 (2.) To protect it against being eaten by animals, 



especially birds, or being carried away by 



wind or water. 



In natural woods large quantities of seed fall to the 

 ground ; some of it is carried by rain-water through the 

 vegetable covering down to the mineral soil, thus find- 

 ing conditions favourable for germination. In artificial 

 sowings the necessary protection is afforded by covering 

 it with earth to a certain depth. 



The thickness of the covering is of considerable 

 importance ; if too thin, the seed is exposed to attacks 

 by animals, is liable to dry up or to be injured by frost ; 

 if too thick, germination is retarded, the seedlings have 

 great difficulty in pushing through the covering, and 

 germination may altogether fail for want of sufficient 

 air. The actual thickness depends on the general con- 

 dition of the seed-bed and the species. It must be 



