112 PRINCIPLES OF STOCK-BREEDING. 



In flowering plants, "it is well known that an 

 over-supply of nutriment will cause an evolution of 

 leaves at the expense of the flowers, so that what actu- 

 ally would have been flower-buds are converted into 

 leaf -buds ; or, the parts of the flower essentially con- 

 cerned in reproduction, namely, the stamens and pistil, 

 are converted into f oliaceous expansions, as in the pro- 

 duction of ' double ' flowers from i single ' ones by cul- 

 tivation ; or, the fertile florets of the ' disk,' in com- 

 posite species, such as the dahlia, are converted into 

 the barren but expanded florets of the 'ray.' And 

 the gardener who wishes to render a tree more pro- 

 ductive of fruit is obliged to restrain its luxuriance by 

 pruning, or to limit its supply of food by trenching 

 around the roots." 



" During the period of rapid growth, when all the 

 energies of the system are concentrated upon the per- 

 fection of its individual structure, the reproductive 

 system remains dormant, and is not aroused until the 

 diminished activity of the nutritive functions allows 

 it to be exercised without injury to them." * 



While the period of rapid growth is not favorable 

 to the development of the reproductive powers, from 

 the great preponderance in the system of the nutritive 

 functions, it will also be found that any marked de- 

 ficiency in the processes of nutrition, as in the decline 

 of life, will result in a decrease and final loss of fer- 

 tility. The age of an animal will thus have an impor- 



1 Carpenter's " Comparatire Physiology," p. 147. Root-pruning, as 

 a remedy for " unf ruitf ulnesse in trees," was recommended by Sir 

 Hugh Plat, in his " Garden of Eden," fifth edition, published in London, 

 1659, p. 162. 



