SEXUAL REPRODUCTION 217 
over, the converse is also true, though it is 
often less easily demonstrated. Fora 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 
