THE PROPAGATION OF PLANTS 187 



as simply a continuation of the growth of the parent 

 in a new location, and generally closely resembles the 

 parent. 



342. Propagation by seeds is commonly practiced 

 with annual and biennial plants and with perennials in 

 which the reproduction of the exact parental form is 

 unimportant, as in the cereals, forest trees and seedlings 

 intended for grafting. This method is also used when 

 variation in the progeny is desired, as in developing 

 new varieties (438). 



This is the most common method of propagating plants. 

 It seemed appropriate to give nearly all of the needed 

 directions for planting seeds in the first two sections of 

 Chapter II. We add, therefore, only a few general rules 

 deduced from the principles there stated. 



(a) The soil in which the seeds are to be planted should 

 be thoroughly crumbled, because the seeds must have 

 access to the oxygen of the air, or they cannot germi- 

 nate (31). 



(6) The well-crumbled soil should be compactly 

 pressed about the seeds, because the seeds cannot absorb 

 moisture rapidly unless the seed-case is in contact with 

 the moist soil particles at many points (27). 



(c) The soil should be moist but not wet enough to 

 puddle (31) ; otherwise the oxygen is likely to be shut 

 out from access to the seeds (34). 



(d) Seeds should be planted no deeper than is neces- 

 sary to insure the proper degree of moisture; otherwise 

 the plantlet expends a needless amount of energy in 

 reaching the surface (47, 50). Very small seeds should 

 be only slightly covered, if at all, and must receive ar- 

 tificial watering when necessary (51). Spores must not 

 be covered with soil at all (52). 



