Varietäten, Descendenz, Hybriden. 67 



The author distinguishes two types of abnormal flower in Begonia 

 a) "primary female" — having a more or less perfectly developed 

 central gynaecium surrounded by rudimentary male organs, b) "pri- 

 mary male" — having a central androecium surrounded by rudi- 

 mentar}»^ female organs. The former is far the commoner type. 



Bearing in mind that sexual differentiation is one of the ear- 

 liest stages in evolution, the problem of sexual evolution in higher 

 plants is not so much a question of the differentiation of sex 

 organs into male and female as the bringing together on one com- 

 mon floral axis of sex organs formally located in different plants or 

 different parts of the same plant. The active factor which brought 

 about this association of sexual organs was probably the necessity 

 for insect as opposed to wind pollination: that determining the 

 central position of the gynaecium was the retention of the embryo 

 in contact with the tissues of the parent plant. Cylologically the 

 central position of the gynaecium is a question of the positions 

 assumed by sex factors in those qualitative divisions which control 

 the segregation of sexual organs. This hypothesis could be tested 

 if future c3^tological research should associate e. g. maleness with 

 the presence of an accessory chromosome. 



The conception of the flower as "primarily male" or female, 

 may be extended to the inflorescence. Thus two types are met 

 with a) terminal male flower with lateral female flowers (as in Be- 

 gonia), b) terminal female flower surrounded by male or herma- 

 phrodite flowers as in Caryophyllaceae The type of flower and 

 inflorescence may vary in same plant. The monoecious type might 

 have arisen by 1) development along female lines as regards the 

 flower, 2) development along male lines as regards the inflorescence. 



Sex dimorphism is a problem of 1) the kind of unils among 

 which sex differentiation occurs, 2) the period in the life history 

 of these units at which this process takes place. Differentiation 

 occurring in germ cell, during flower development, or during the 

 development of sex organs on the floral axis will determine whether 

 the sex condition of the plant is dioecious, monoecious or herma- 

 phrodite. As to whether the factors which control sex segregation 

 in monoecious plants are the same as those which determine sex in 

 dioecious plants, the author argues that the distinction is chiefly on 

 the time of segregation. 



The secondary sex characters tend to follow the primär}?- sex 

 of the flower in Begonia. The association between primary and 

 secondary sex characters shown in segregation seems less intimate 

 in plants than in animals. W. Neilson Jones. 



Everest, A. E., Recent chemical investigations of the 

 anthocyan pigments and their bearing upon the pro- 

 duction of these pigments in plants. (Journ. of Genetics. 

 IV. p. 361—367. 1915.) 



Important points of recent chemical investigations of the antho- 

 cyan pigments are summarised. 



Up to the present the concensus of opinion has been in favour 

 of the theory that anthocyans are produced by oxidation of yellow 

 pigments of the flavone or flavonol series. The author considers 

 that it should be realised now that these ideas have failed to stand 

 the test of chemical investigation in every case that has been exa- 

 mined in a chemically satisfactory manner. The author gives briefly 



