Vol. 36 



BULLETIN 



No 4 



OF THE 



*- 



TORREY BOTANICAL CLUB 



APRIL, 1909 



Sex In dioecious plants 



Chester Arthur Darling 

 (with plates 12-14) 



Probably no other question has received such universal attention 

 among biologists as that of heredity, and perhaps no avenue of 

 approach in solving this question promises at present greater results 

 than that of the determination of sex. It has been generally be- 

 lieved until within the last few years that sex was largely deter- 

 mined by surrounding conditions, such as food, heat, light, or 

 other external factors. . This belief was strengthened by such 

 work as that of Prantl ('81) on the ferns. When prothallia were 

 cultivated with abundant nutriment only archegonia developed, 

 whereas antheridia were formed on those poorly nourished. It 

 should be noted however, that the prothaHia with which he worked 

 were not strictly dioecious, but had a '' tendency to dioeciousness.'^ 

 Similar experiments w^ere performed upon other groups of 

 plants, as well as upon animals, with the same general results. 

 There can be little doubt that environmental factors do influence 

 either directly or indirectly the development of sexual organs in 

 plants where both tendencies exist. But recent and more care- 

 ful experiments have shown that in strictly dioecious forms such 

 factors do not determine, at least in the life history of the indi- 

 vidual, which sex shall develop. 



Strasburger ('oo) working with plants and Cuenot ('99) vvith 

 animals, have carefully reviewed the evidence and in their own ex- 

 periments have shown that in dioecious forms sex is not determined 

 bv environmental factors but is inherent in the germ cells. 



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177 



