the Determination of Sex in Plants. 437 



character which is transmitted through the pollen grain were also 

 manifest in it, both white and grey-green pollen grains should 

 have been produced in equal numbers. In fact, as Strasburger 

 remarks, Correns' result proves that the sporophyte determines 

 the colour-character exhibited by the dependent gametophyte. 



Sex in the gametophyte, being then a character derived solely 

 from the parent sporophyte and independent of the sex-character 

 carried by the germ cells, is probably not comparable to those 

 somatic characters of the gametophyte which are predetermined 

 and not influenced by the environment, that is, to the somatic 

 characters of, for example, the gametophyte of the Bryophyta, — 

 characters which are sufficiently definite to admit of their use in 

 classification 1 . 



The differentiation between the megasporangia and micro- 

 sporangia of heterosporous plants is exactly analogous with that 

 between archegonia and antheridia (p. 435). Such analogy suggests 

 that the determining factor is the same in each case — an effect of 

 nutrition. 



In dioecious plants the development either of megasporangia 

 or of microsporangia would be the expression of a difference 

 between the nutrition of the two forms. But this difference is 

 not merely quantitative. Male and female may be looked upon 

 as physiological varieties characterized by distinct physiological 

 processes, in the male tending toward subdivision and the forma- 

 tion of antherozoids, in the female toward arrest of division, the 

 storage of food and the nutrition of the embryo. These processes 

 retain their distinctive features in spite of changes in the en- 

 vironment. 



Castle regards hermaphrodite organisms as "sex-mosaics," using 

 the analogy of spotted mice as a mosaic form combining two 

 colour-characters. The use of this term, particularly when an 

 analogy with mosaic mice is drawn, rather leads one to suppose 

 that hermaphrodite races are to be regarded as having arisen 

 through the formation of mosaic gametes by individuals who 

 owed their origin to dioecious parents. 



But among the Pteridophyta no instance is known of a plant 

 which, while retaining the primitive independent condition of the 

 gametophyte, also possesses the dioecious character in the sporo- 

 phyte. So that it seems more logical to regard the primitive 

 hermaphrodite as undifferentiated in respect of the separation of 

 the sexes, which only appears at a higher stage of evolution, and 

 is of the nature of a discontinuous variation (Bateson ('94)). 



1 The characters of the gametophyte in Pteridophyta are so entirely under the 

 influence of environment that any attempt at classification based upon them at once 

 breaks down (Bauke (78), Heim ('96)). 



