106 Plant-Breeding 



"and the various compound rhythms resulting from their 

 combinations, are in such adjustment as to balance the 

 actions to which the organism is subject. There is a 

 constant or periodic genesis of forces which, in their kind, 

 amounts, and directions, suffice to antagonize the forces 

 which the organism has constantly or periodically to bear. 

 If, then, there exists this state of moving equilibrium 

 among a definite set of internal actions, exposed to a 

 definite set of external actions, what must result if any of 

 the external actions are changed ? Of course there is no 

 longer an equilibrium. Some force which the organism 

 habitually generates is too great or too small to balance 

 some incident force; and there arises a residuary force 

 exerted by the environment on the organism, or by the 

 organism on the environment. This residuary force, this 

 unbalanced force, of necessity expends itself in producing 

 some change of state in the organism." 



The good results, therefore, are processes of adaptation, 

 and when adaptation is perfect or complete, the plant may 

 have gained no permanent advantage over its former 

 conditions, and new crossing or another change may be 

 necessary ; yet there is often a permanent gain, as when a 

 plant becomes visibly modified by change to another cli- 

 mate. Now this adaptive change may express itself in 

 two ways : either by some direct influence on the stature, 

 vigor, or other general characters ; or directly on the 

 reproductive powers, by which some new influence is 

 carried to the offspring. If the direct influences become 

 hereditary, as observations seem to show may sometimes 

 occur, the two directions of modification may amount, 

 ultimately, to the same thing. 



