524 



MOSSES AND FERNS 



CHAP. 



sporangium of the strobilus. This is much larger than the 

 microsporangia, and the sporophyll correspondingly large. 

 In other species, e. g., S. apus, there may be 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 meristem of the same, X450; s, the apex of the main axis; s', a young 

 lateral branch; B, B, young leaves; L, ligula 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; f, one of the trabeculs. 



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 the strobilus. Miss Lyon made some interesting 

 observations upon the development of the sporangia in S. apus 

 and S. rupesfris. In the latter species the strobili begin to de- 



