lO Weiss, Researches on Heredity in Plants. 



characters, following Mendel's laws of inheritance, and 

 some experiments have been undertaken to elucidate this 

 problem. 



In the vegetable kingdom the problem is complicated 

 by the fact that the flowering plants, which are the most 

 easy to experiment with, are generally hermaphrodite, 

 i.e., bear both the pollen and the ovules in the same 

 flower. Experiments have, however, been made by 

 Correns' on the Brj'ony, which has unisexual flowery 

 monoecious in Bryonia alba and dioecious, i.e..o\\ separate 

 plants, in Bryonia dioica. The results of his experiments 

 lead him to the conclusion that in Bryonia dioica the 

 male is heterozygous in sex, maleness being dominant, 

 while the female plant is homozygous. The mating of 

 the two would therefore give an equal number of male 

 and of female plants. Professor Bateson on the other 

 hand considers that the results obtained by Correns 

 might possibly be explained by taking femaleness to be 

 dominant, and the female to be heterozygous in sex. 

 This would be more in agreement with certain cases in the 

 animal kingdom, which seem only explicable by such a 

 theory. To quote Bateson, " the evidence from the 

 descent of the dominant sex-limited diseases such as 

 colour-blindness, and of the horns in sheep is also con- 

 sistent with the same view, namely, that femaleness is 

 due to the presence of a dominant factor. For in these 

 examples there is evidently some additional element 

 present in the female which inhibits or suppresses the 

 operations of the sex-limited dominant, and that addi- 

 tional element may not improbably be the factor for 

 femaleness.'"' 



As an example of the practical application of 

 Mendelian principles, I may, in conclusion, refer to the 



^ Correns, C. Bestimmung und \'ererbang des Geschlechtes, Leipzig, 

 Borntraeger, 1907. 



