PROPAGATION OF PLANTS. 217 



mcnt, Natural Selection preserves and accumu- 

 lates them ; when they are not beneficial, Natural 

 Selection discards them ; that is, the plant pos- 

 sessing these beneficial variations has a better 

 chance to survive and perpetuate the species, 

 U'hile the plant ivhose variations are less bene- 

 fjcial "ivill probably perish ; Jience, that variation 

 is not perpetuated. 



Everywhere in nature the competent are pre- 

 served and the incompetent are discarded. In 

 other words, the power of an organism to vary 

 is the measure of its adaptability to environ- 

 ment. It is by the preservation, transmission, 

 and accumulation of these variations that new 

 varieties are formed among uncultivated plants. 

 Man takes advantage of this fact, and by artifi- 

 cial selection preserves those characteristics of 

 the plant which are beneficial to him, thus orig- 

 inating new varieties among cultivated plants. 



It takes many generations for these varieties 

 to become fixed types. The time required for 

 the fixation of types, however, depends upon 

 several conditions, one of which is (i) the ten- 

 dency of the plant to vary. The more variable 

 the plant, the more difficult will be the fixation 

 of the type ; for, although it will be easier to 

 find individual plants having the desired char- 

 acteristics, on account of this variability there 

 will be less assurance that these characteristics 

 will be generally reproduced in the subsequent 



