GEKEEAL PRINCIPLES AND METHODS. 139 



penetrated by the young rootlets. Seeds of our common 

 forest trees, when they fall upon the thick mat of old 

 leaves, usually fail to grow because tb^ young roots can- 

 not penetrate through the tough, fibrous material under- 

 neath them ; but let these seeds be scattered along the 

 roadsides, or in the open fields, or wherever they can come 

 in direct contact with moist soil, and they soon show 

 that they have found congenial conditions for growth. 



No general rule can be given in regard to the depth 

 for covering seeds, not even one that would apply to all 

 the members of the same family of plants, because they 

 frequently differ in their habit of growth, as, for in- 

 stance, in Peas and Beans, the cotyledons of the former 

 remaining under ground and those of the latter being 

 lifted above the surface in the elongation of the stem ; 

 consequently we can safely cover a small variety of the 

 Pea much deeper than the largest variety of the Bean, 

 although both are closely allied dicotyledonous plants. 

 Similar variations also occur among the monocotyledon- 

 ous seeds, the plumule or stem usually rising in the form 

 of a cylindrical column, whether they are of the size of the 

 giant Cocoanut, or of Rye, Wheat, or the stUl smaller 

 grasses. Depth, however, must be varied somewhat, 

 according to the nature of the soil in which seeds are 

 sown, for a stem that would readily push up tlirough an 

 inch or two of vegetable mold or of sand, might be un- 

 able to pierce the same thickness of compact loam, or 

 tough, hard clay. 



When seeds have once begun to grow, they cannot be 

 again reduced to a dormant state without causing their 

 destruction; this should always be borne in mind, for 

 from this cause alone more seeds are annually destroyed 

 than from any other. As they are usually hidden in 

 the soil, we are very likely to neglect giving them an 

 ample supply of moisture at their time of greatest need. 



The soil in which seeds are sown should be made fine 



