46 GENEBAL PEINCIPLES. 



lie in the ground all summer, and possibly germinate the 

 spring following. If cherry seeds are kept dry fur any 

 length of time, say two or three months, they will not 

 germinate the season following ; and peaches and plums 

 have actually to be in the ground all winter, under the 

 action of frost, to insure their germination the spring fol- 

 lowing. Seeds will germinate much quicker when freshly 

 gathered than after they have dried, because heat, mois- 

 ture, and air have easier access to them, and act more 

 quickly on them. These facts, of which all are well 

 aware, show the necessity for moisture and the nature of 

 its influence. 



2d. Heat is the next most important element. Seeds do 

 not grow in winter. We sow our apple, pear, peach, and 

 plum seeds in November ; but they show no signs of ger- 

 mination until a change of season. When the warmth of 

 spring penetrates the soil, it reaches the seed, and, in con- 

 nection with the moisture already imbibed, induces what 

 we usually call fermentation. This chemical process ex- 

 cites the vital energies of the germ, decomposes the 

 mealy part of the seed, and prepares it for the temporary 

 nutrition of the young plant. 



3d. Air. Although seeds may have heat and moisture 

 in the requisite proportions, still it has been proved by 

 many experiments, that without air, germination cannot 

 take place. 



Practical cultivators are aware that seeds planted too 

 deeply do not grow ; many kinds will lie buried in the 

 ground for years without growing, and when turned up 

 near the surface will germinate immediately. It is the 

 oxygen of the air that constitutes its importance ; it pro- 

 duces, by forming new combinations with the gases con- 

 tained in the seed, that chemical process which converts 

 the starch into sugar and gum, as we observe in ordinary 

 cases of fermentation. 



