106 JOHN H. SCHAFFNER Vol. XXII, No. 4 



phism, as a chromosome difference, for example. The sporophyte 

 is nonsexual in expression in every respect although it carries 

 sexual potentialities in its cells in a latent condition. These 

 potentialities become evident in such abnormal cases as 

 apospory. The sporophyte in normal conditions is entirely 

 neutral in respect to sex, while the gametophyte shows all 

 gradations from hermaphrodites with closely associated sex 

 organs to extreme, unisexual individuals. 



10. The lowest stage of this series is represented by species 

 with haploid, hermaphroditic gametophytes having the ovaries 

 and spermaries closely associated. Examples: many liverworts 

 and mosses (synoicous condition). 



11. Haploid gametophytes which are hermaphrodites, but 

 which have distinctly differentiated male and female areas. 

 Examples: many ferns, mosses, and liverworts as Lophocolea 

 heterophylla (paroicous condition). 



12. Haploid hermaphroditic gametophytes which have the 

 male and female organs on distinct branches or axes. Examples: 

 many liverworts, bog-mosses, and mosses, as Phascum cus- 

 pidatum (autoicous condition). 



There are, of course, practically all possible intergradations 

 between stages 10, 11 and 12. 



13. Haploid gametophytes differentiated into male and 

 female individuals (unisexual) but which may be reversed in 

 sex, either normally through age and growth or artificially by 

 being subjected to the proper environment. 



Examples : Equisetum arvense, Matteuccia struthiopteris. 



Note: There are also many species especially among the 

 liverworts and mosses which have part of the individuals uni- 

 sexual and part hermaphroditic (imperfectly unisexual), as 

 Cephalozia curvifolia. 



14. Haploid gametophytes differentiated into male and 

 female individuals and these apparently not reversible by 

 known experimental means or reversible only rarely; often 

 showing a high degree of sexual dimorphism; in a few cases 

 at least, but apparently not often, with a difference in size of 

 synaptic chromosomes which are associated with the two sexes. 



Examples: Sphaerocarpus, Marchantia, Polytrichum. 

 Note: Marchantia polymorpha is occasionally hermaph- 

 roditic. 



