THE GKEAT GROUPS OF PTERIDOPHYTES 



165 



The solitary sporangium appears in the axils (upper 

 angles formed by the leaves with the stem) of the leaves 

 and sporophylls, but arise from the stem instead of the 



Fig. 139. Selayinella Martensii: A, branch bearing strobili; B, a microsporophyll 

 with a microsporanginm, showing microspores through a rupture in the wall; C, 

 a megasporophyll with a megasporangium ; I), megaspores ; E, microsporea. — 



GOLDBERGEB. 



