ON PROP A GA TION B T SEED. 209 



it is accompanied, the vital power of the seed, and the nature of the 

 species. The seeds of aquatic plants vegetate when immersed in water, 

 and the plants live and attain maturity in that element ; but those of 

 land plants, though they will vegetate in water, yet if the plants be not 

 removed immediately after germination, they will become putrid and 

 die. In general, the most favourable degree of moisture for newly- 

 sown seeds, is that which a free soil holds in its interstices. Clayey 

 soil will retain too much moisture for delicate seeds, and sand too 

 little ; but an open, free loam will attract and retain the proper quan- 

 tity for all seeds, excepting those which are very small and very deli- 

 cate ; and for these a mixture of peat loam and fine sand will retain 

 just moisture enough, and no more. With all delicate seeds it is 

 better rather to have too little moisture than too much ; and with all 

 seeds whatever, it is of great importance to preserve the degree of 

 moisture uniform. For this purpose, in the open garden, newly-sown 

 delicate seeds are shaded or covered by different means, such as sowing 

 them on the north sides of hedges or walls, interposing hurdles placed 

 upright or horizontally between the sown seeds and the sun, covering 

 with mats, or branches, or litter, or, in the case of very small seeds, 

 with moss. The more tender kinds are also sown in frames, or under 

 hand or bell-glasses, by which evaporation is prevented or checked, and 

 a steady degree of moisture effectually maintained. 



The water requisite to cause old seeds to germinate should be more 

 gradually given to them than that given to vigorous young seeds ; 

 because the power of absorbing water in old seeds is not diminished in 

 the same proportion as their power of decomposing it. When old seeds 

 are placed in moist soil, they are consequently very liable to rot; 

 more especially if the temperature be not somewhat higher than new 

 seeds of the same species usually require. Hence, old seeds should 

 be sown in a much drier soil than new seeds, and should be supplied 

 with water much more sparingly, or left to absorb it from the 

 atmosphere. 



The depth to which a seed is buried in the soil has, for its chief 

 object, the maintenance of a due degree of moisture, but another pur- 

 pose is to exclude the light, and to give the future plant a better hold 

 of the ground ; though there is no seed whatever that will not vege- 

 tate on the surface, if that surface be kept uniformly moist and shaded. 

 It may be assumed that every seed will vegetate and establish itself in 

 the soil, if buried to its own thickness ; but the experience of gar- 

 deners proves, that some large seeds, such as leguminous seeds, nuts, 

 &c., make better plants when buried much deeper. 



The degree of heat most favourable for the germination of seeds 

 may be considered as that best adapted for the growth of the parent 

 plants ; and hence if the native country of any plant is known, it may 

 be assumed that its seeds will germinate best in the temperature of 

 the spring, or growing season of that country. Some seeds of cold 

 climates, such as those of the * common annual grass, chickweed, 

 groundsel, &c., will germinate in a temperature little above the freez- 

 ing point ; but, in general, few northern plants will germinate under 



