2S6 SANSOME 



females in the stylar half of an ovary and a larger proportion 

 of males in the other half (Correns). The male-determining 

 pollen tube of Melandrium is longer lived and has greater re- 

 sistance to alcohol fumes than the female-determining. It is 

 interesting to note that the degree of difference in growth rate 

 and vitality of the alternative sex-determining pollen grains 

 depends on the race of Melandrium used (Correns). 



In conclusion, a number of facts indicate that sometimes the 

 interaction between the cytoplasm and the nuclear factors pro- 

 duces sub-gynoecious plants in hermaphroditic species [Linum 

 usitatissimum (Gairdner, Chittenden and Pellew), Satureia 

 hortensis (Correns), Cirsium oleracium and C. canum (Correns)] . 

 There is also a connection between sex and morphological and 

 physiological sterility. This cursory summary indicates certain 

 distinct trends in plants with regard to sexuality. Together with 

 the gradual encroachment of sex differentiation into the diploid 

 phase there is an increase in potency of the genetic factors over 

 the environmental and extra-nuclear factors, and also there is 

 a condensation of the genetic factors. 



BIBLIOGRAPHY 



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somenbestand," liereditas, 10. 

 Allen, C. E. (1917) '' A Chromosome Difference Correlated with Sex Differences 



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 Baur, E. (1912) " Ein Fall von geschlechtsbegrentzer Vererbung bei Melandrium 



album" Zeit. ind. Abst. u. Verer., 8. 

 Belar, K. (1925) " Der Chromosomenbestand der Melandrium zwitter," Zeit. ind. 



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 Blackburn, K. B. (1924) " The Cytological Aspects of the Determination of Sex 



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schlechter beim Saurampfer. Rumex acetosa," Biol. Zentral, 42. 

 — (1928) " Bestimmung, Vererbung, u. Verteilung des Geschlechts bei der 



hbheren Pflanzen." Handb. der Vererbungwiss., Borntrager. 

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