216 PLANT LIFE 
its nutrition. It is possible to maintain the 
plant, apparently for an indefinite period, in 
a state of vegetatively active growth. On 
the other hand, it may with almost equal 
certainty be compelled to enter on the 
sexually reproductive phase of its life. A 
sudden starvation, if previously well nourished, 
and so long as the organisms are exposed to 
light, will at once bring about the change 
that leads to the formation of gametes. But 
we may at once confess that we do not as 
yet understand how these conditions work 
in producing the observed effects. Nor are 
we able to form a clear idea as to why the 
addition of nutritive salts to the water in 
which the chlamydomonas is living suffices 
at once to arrest sexual development, and to 
switch the life processes back on to the 
vegetative course; so much so, indeed, that 
even gametes can develop independently, 
and in a vegetative manner, 7. e. without any 
sexual union. 
But the effects of sudden starvation on 
previously well-nourished organisms are well 
known to conduce to the development of 
sexual reproductive organs. In a chlamydo- 
monas the organism and the sexual cell are 
practically identical, and it is in the highest 
degree suggestive to find that what stimulates 
the production of sexual organs in a complex 
and highly differentiated plant will also cause 
the undifferentiated primitive one also to 
enter on a sexual condition or phase. More- 
