HYPERTROPHY. 449 



of power ill the ovules, or in the vegetable force, 

 by which they are excited, and not in the pollen 

 grains themselves ; — an inference supported by 

 analogy in the animal kingdom." 



In the fruit tree this hypertrophy is often seen 

 in the unnatural growth of wood, induced by a 

 highly nitrogenous soil. The force of this growth 

 is often so great, that if any fruit-buds are formed, 

 they are changed into wood-buds the next spring, 

 and shoots start from them. This disease can be 

 remedied by severe summer pinching, as described 

 in the chapter upon pruning, and by root-pruning, 

 which will effectually check undue luxuriance. 

 This condition is often induced by too severe and 

 injudicious spring pruning. As was noticed in 

 another chapter, the limbs which proceed from the 

 buds at the base of the shoots do not produce fruit 

 as readily as those from the terminus, or even at 

 midway ; and, therefore, by pruning back to these 

 at the base, the fruit-grower is constantly producing 

 either partial or total sterility. 



In some cases sterility is caused by the monacious 

 character of the plant (or the possession of only 

 one of the sexes, the other being absent or sessile), 

 and consequently by a defective fecundation, or 

 none at all. This is particularly the case with 

 strawberries. Some of our most valuable varieties 

 are utterly unable to produce a large crop without 

 the presence of other varieties in the line, or near 

 38* 



