CHAPTER XIV 

 CONDITIONS OF GAMETE FORMATION IN PLANTS AND ANIMALS 



In all organisms the production of the gametes or sexual cells, 

 the condition known in the higher forms as sexual maturity, is 

 apparently associated with certain other physiological conditions 

 which, at least in the higher animals, are characteristic of relatively 

 advanced stages of development. The present chapter is an 

 attempt to establish a general foundation for the interpretation of 

 the various data of observation and experiment. This foundation 

 is in brief the view that the production of gametes is simply one 

 feature of the orderly development of the organism and is therefore 

 associated with certain conditions in other organs and is related 

 to processes of differentiation and senescence in the organism as a 

 whole. 



CONDITIONS OF GAMETE FORMATION IN THE ALGAE AND FUNGI 



It was formerly believed that the essential factors determining 

 reproduction, and particularly gametic or sexual reproduction in 

 plants were internal, and that external factors had but little to do 

 with the process. But various investigators, and particularly 

 Klebs, have demonstrated that the sequence of events in the life 

 cycle of plants can, to a very large extent, be controlled by external 

 factors. Klebs's work along this line has been discussed in chap, x 

 in connection with agamic reproduction (pp. 249-52), and here only 

 certain points which concern the formation of gametes need be 

 considered. Klebs mentions the fact that where spore formation 

 or gamete formation or both occur in cultures of Vaucheria and 

 Saprolegnia, in addition to what he calls growth, which is what I 

 have called vegetative reproduction, these more specialized repro- 

 ductive processes occur on the older parts of the plant body and 

 the vegetative on the younger. He also concludes that the attain- 

 ment of a certain concentration of the organic substances in the 

 plant is an essential condition for such reproductive processes and 

 that for gametic reproduction the concentration must be higher 



364 



