524 



MOSSES AND FERNS 



CHAP. 



sporangium of the strobilus. This is much larger than the 

 microsporangia, and the sporophyll correspondingly large. 

 In other species, c. g., S. apiis, there may l)e several macrospo- 

 rangia. According to Hieronymus the position of the stro- 

 bilus conditions to some extent the development of macrospo- 

 rangia, which are either basal, or in that part of the strobilus 



Fig. 303. — Selaginella Kraussiana. Horizontal section of the apex of the stem, X77', B, 

 the apical meristeni of the same, X450; s, the apex of the main axis; s', a young 

 lateral branch; B, B, young leaves; L, lig\ila of the leaf; C, D, longitudinal sec- 

 tions of the base of older leaves, X450; i, i. lacuna surrounding the vascular bun- 

 dles of the stem; t, one of the trabeculae. 



nearest the ground. Thus in dorsiventral strobili they are de- 

 veloped on the ventral side; in pendent ones they may form at 

 the apex of tlie strobilus. Aliss Lyon made some interesting 

 observations upon the development of the sporangia in ^. apiis 

 and vS'. rupestris. In the latter species the strobili begin to de- 



