456 LAWS OF MULTIPLICATION. 



ences. When treating of Genesis inductively, we reached the 

 generalization that " the products of a fertilized gerra go 

 on accumulating by simple growth, so long as the forces 

 whence growth results are greatly in excess of the antagonist 

 forces ; but that when diminution of the one set of forces, or 

 increase of the other, causes a considerable decline in this ex- 

 cess, and an approach towards equilibrium, fertilized germs 

 are agaiu produced.*' (§ 78.) It was pointed out that this 

 holds of organisms which multiply by heterogenesis, as 

 well as those which multiply by homogenesis. And plants 

 were referred to as illustrating, both generally and locally, 

 the decline of agamic multiplication and commencement of 

 gamic multiplication, along with a lessening rate of nutrition. 

 Now the many cases that are given of fruitfulness caused in 

 trees by depletion, are really cases of this change from 

 agamogenesis to gamogenesis ; and simply go to prove that 

 what would naturally arise when decreased peripheral growth 

 had followed increased size, may be brought about artificially 

 by diminishing the supply of materials for growth. Cramp- 

 ing its roots in a pot, or cutting them, or ringing its branches, 

 will make a tree bear very early: bringing about a pre- 

 mature establishment of that relative innutrition which 

 would have spontaneously arisen in course of time. Such 

 facts by no means show that in plants, sexual genesis in- 

 creases as nutrition diminishes. When it has once set in, 

 sexual genesis is scanty or imperfect unless nutrition is good. 

 Though the starved plant may blossom, yet many of its 

 blossoms will fail ; and such seeds as it produces will be ill- 

 furnished with those enveloping structures and that store of 

 albumen, &c., needed to give good chances of successful germi- 

 nation — the number of surviving offspring will be diminished. 

 Were it otherwise, the manuring of fields that are to bear 

 seed-crops, would be not simply useless but injurious. Were 

 it otherwise, dunging the roots of a fruit-tree would in all 

 cases be impolitic ; instead of being impolitic only where the 

 growth of sexless axes is still luxuriant. Were it otherwise, 



