23a TEMPERATURE OF SOIL IMPORTANT. 



The latter practice is not, however, merely for the sake of 

 covering the seed with the smallest possible quantity of soil, 

 but has for its object the separation of seeds to such a dis- 

 tance, that when they germinate they may not choke up each 

 other. If seedlings, like other plants, are placed so near 

 together that they either exhaust the soil of its organizable 

 matter, or overshadow each other so as to hinder the requisite 

 quantity of light, some will die in order that the remainder 

 may live ; and this, in the case of rare seeds, should, of course, 

 be guarded against very carefully. 



" The injuriousness of covering seed with too much earth arises less 

 from the superinciunbeiit pressure of the soil, than from the exclusion 

 of atmospheric air, which is quite indispensable to germination. The 

 seed of the common Flax comes up at different periods, according 

 as it is planted in one, two, or three inches depth of soil ; if it be 

 sown four inches below the surface it will not come up at all. Not that 

 air does not penetrate to this depth in the soil, but the quantity of air 

 will very much depend on the looser or denser character of the soil. 

 Thouin, in his Cours d' Agriculture, remarks that small seeds should 

 be covered only a liue deep with earth, and this spread over very 

 loosely ; seeds of the size of Peas and Beans, about three-quarters of an 

 inch deep, and the bulky seeds of our fruit-trees, such as the Apricot, 

 Nuts, Peaches, Almonds, with from two to three inches of soil." — 

 German Translation. 



With regard to the temperature to which a seed should be 

 subjected, in order to secure its germination, this, undoubtedly, 

 varies with different species, and depends upon their petjuliai' 

 habits, and the temperature of the climate of which they are 

 native. So far as general rules can be given upon such a 

 subject, it may be stated tiiat the temperature of the earth 

 most favourable for germination is 50° to 55° for the seeds of 

 cold countries, 60° to 65° for those of "greenhouse plantSj" 

 and 70° to 80° for those of the torri-d zone. We are assured 

 by Mr. Cowan, that although the Cocoa-nut is cultivated in 

 the mountainous parts of Jamaica; where the atmospheric 

 temperature varies from 60° to 90°, it only assumes the 

 characteristic grandeur of Palms, and can only be propagiated 

 with certainty, by the seaside, where the heat of the Soil exceeds 

 1 90°. And it may be laid down as a rule, in sowing tropical 



