160 APPLICATION OF PRINCIPLES. 



ration are impeded, and it is unable to decompose the 

 water it absorbs, which collects in its cavities and be- 

 comes putrid. There must, therefore, be some 

 amount of water, which to the dormant as well as the 

 vegetating plant is naturally more suitable than any 

 other ; and experience shows that quantity to be just 

 so much as the particles of earth can retain around 

 and among them by the mere force of attraction. To 

 this is to be ascribed the advantage derived from 

 those mixtures of peat, loam and sand, which gar- 

 deners prefer for their seedlings ; the peat and sand 

 together keep asunder the particles of loam which 

 would otherwise adhere and prevent the percolation 

 of water ; the loam retains moisture with force enough 

 to prevent its passing off too quickly through the 

 wide interstices of sand and peat. If, during the de- 

 licate action of germination, the changes that the seed 

 undergoes take place without interruption, the young 

 plant makes its appearance in a healthy state ; but, 

 if by irregular variations of heat, light and moisture, 

 the progress of germination is sometimes accelerated 

 and sometimes stopped, the fragile machinery upon 

 whioh vitality depends may become so much de- 

 ranged as to be no longer able to perform its actions, 

 and the seed will die. It is for the purpose of secur- 

 ing uniformity in these respects, that we employ, in 

 delicate cases, the steady heat of a gentle hot-bed, 

 shaded ; and, in all cases whatever, the assistance of 

 a coating of earth scattered over the seed. 



Under what depth of earth seed should be buried 

 must always be judged of by the experience of a gar- 



