182 Principles of Plant Culture. 



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 unimport- 

 ant, 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 b). 



343. Propagation by Division of the plant is used when it 

 is desired to reproduce the exact parental form, as in fruit- 

 and the finer ornamental trees, many flowering plants, 

 etc. ; in certain plants that are more readily multiplied 

 by division than by seeds, as mint and many other per- 

 ennial herbs; and in other plants that rarely or never 

 produce seed, as the horse-radish, sugar cane, banana, etc. 



A PROPAGATION BY SEEDS 



344. 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 sec- 

 tions of Chapter II. We add, therefore, only a few 

 general rules deduced from the principles there stated. 



a The soil in which seeds are to be planted should be 

 thoroughly crumbled, because the seeds must have access 

 to the oxygen of the air, or they cannot germinate (31). 



b 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 b). 



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 (35). 



