CHAPTER V. 



OF SEED-SOWING. 



When a seed is eommitted to tlie earth, it undergoes certain 

 chemical changes before it can develope new parts and grow. 

 These changes are brought about by heat and water, assisted 

 by the absence of light. In many seeds the vital principle is 

 so strong, that to scatter them upon the soil, and to cover 

 them slightly with earth, is sufficient to insure their speedy 

 germination; but in others the power of growth will only 

 manifest itself under more favourable conditions : it is, there- 

 fore, necessary to consider well upon what the circumstances 

 most suitable to gerniination depend. 



Moisture is necessary, but not an unlimited quantity. If a 

 seed is thrown into water and exposed to a proper tempera^ 

 ture, the act of germination will take place : bat, unless the 

 plant is an aquatic, it will speedily perish ; no doubt because 

 its powers of respiration are impeded, and it is unable to 

 decompose the water it absorbs, which collects in its cavities 

 and becomes 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 retaia 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 gardeners 

 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 



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