192 Principles of Plant Culture. 



ure rapidly unless the seed-case is in contact with the 

 moist soil particles at many points (27 b). 



e—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 (50, 47). 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) . 



B — Propagation by Division. 



345. "We have seen that a part of a plant, placed un- 

 der favorable conditions, is usually capable of develop- 

 ing a complete plant (340). A section or cutting of 

 the stem, for example, that has no roots' at the time it 

 is cut off, may be caused to form roots, and thus be- 

 come a complete plant. A cutting of a root may also 

 put forth a bud, which in turn may develop into a 

 shoot, and form leaves, flowers and fruit. Again, we 

 have seen that portions of cambium from different, 

 nearly-related plants may unite by growth (69), which 

 enables us to change undesirable sorts into valuable 

 ones by grafting (383). These and certain other meth- 

 ods of multiplying plants, come under propagation by 

 division. 



In propagation by division, the presence of at least 

 one' healthy growing point (66) in the part selected for 

 the propagation is generally essential to success and is 

 always helpful. 



