IN THE BRYOPHYTA 



205 



An examination of the origin of this dorsiventrality, thus seen in an 

 organ which is as a rule of radial construction, has shown that it appears 

 relatively late in the course of the individual development, and is thus 

 secondary. The young embryo of Fnuaria is a radially constructed 

 spindle, and the inequality only appears as the capsule approaches 



l-'n;. 103. 



3. Diagrammatic louijitudiniil section through the green capsule of Physcomitriutii 

 pvi forme. X 14. 5. Median longitudinal section through the mature green capsule 

 i if I'unaria. hygroinctrica. X 20. 8. Profile view of mature capsule of the dorsiventral 

 i .ipsule of Bii.vf'aiiniiii aphylla. 9. Median longitudinal section of the same capsule ; 

 /=cylindrical air-space ; at s the stomata. X 10. 10. Transverse section of the sami 

 i .ipsule, about the middle. X 9. (After Haberlandt.) 



maturity. In the Buxbaumieae the dorsiventrality is more marked : 

 the sporogonium of Diphvsciidn shows when young a characteristically 

 radial cell-net ; but external examination of even young sporogonia shows 

 that the dorsiventral form of the capsule as a whole can be recognised 

 comparatively early : a condition which accords with its very pronounced 

 lopsidedness when mature. An enquiry into the circumstances which 



