SEXUAL REPRODUCTION 217 



over, the converse is also true, though it is 

 often less easily demonstrated. For a reversal 

 of the conditions that led to the development 

 of the sexual state will arrest it, and cause not 

 only lowly, but many of the higher plants 

 to resume their vegetative growth. Some of 

 the malformations often seen in flowering 

 plants, as the consequence of injudicious 

 manuring, represent the results of the 

 antagonism between the sexual and vegetative 

 functions. 



But in the more specialised plants, where 

 the sexual and other reproductive cells are 

 different from the general mass of the body 

 cells, the sexual elements themselves are 

 more limited in their range of development. 

 We can, in favourable instances, so influence 

 the plant as to determine whether or not it 

 shall form sexual organs. But where once 

 the sexual cells are formed, these can seldom be 

 induced to develop further, unless they unite 

 in appropriate pairs. For some reason the 

 chemical processes no longer run in the 

 direction of growth and development. They 

 result in death and disintegration unless a 

 sexual fusion occurs. 



We do not as yet know why this should 

 be so, but the experimental work of recent 

 years has taught us that by suitably altering 

 the conditions of chemical action within the 

 protoplasm of the gamete, and especially by 

 appropriately regulating the oxidative pro- 

 cesses, the cell will again be able to resume 



