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, *. 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- 



