64 VITAL ACTIONS. 



the most favourable conditions ; and under unfavour- 

 able circumstances, tbe age at whicli it fructifies is so 

 much increased as to have given rise to the vulgar 

 belief that it flowers only after a hundred years. This 

 very curious subject has been little investigated, and 

 we have no comparative statements of the ages at 

 which different species begin to bear ; but the fact is 

 certain. It is often, however, in the power of man to 

 advance or retard these periods artificially. What- 

 ever produces excessive vigour in plants is favour- 

 able to the formation of leaf-buds, and unfavourable 

 to the production of flower-buds ; whUe, on the other 

 hand, such circumstances as tend to diminish luxu- 

 riance, and to check rapid vegetation, without affect- 

 ing the health of the individual, are more favourable 

 to the production of flower-buds than of leaf-buds. 

 Thus, a plant in a sterile soil and exposed situation 

 flowers sooner and more abundantly than one in a 

 rich and shaded place ; young vigorous plants flower 

 later and less abundantly than old ones. In India 

 and China, fruit trees are made to bear by cutting 

 their roots, or exposing them periodically to dryness ; 

 and in this country the same practice is observed, es- 

 pecially with the fig-tree. An apparent exception to 

 this law is found in the fact that a seedling fruit tree 

 may be made, by grafting upon any old stock, to bear 

 flowers at an earlier age than it otherwise would have 

 done ; for the effect of grafting it thus is certainly not 

 to render it less vigorous, but the contrary. But it 

 is probable that all these facts arise out of one com- 

 mon law, which is, that the period when a plant be- 



