CALAMOSTACHYS 



57 



heterosporous Calamarian cone, and some of the species 

 from the Continent show the same phenomenon. The 

 difference between microspores and megaspores, though 

 well marked, is, however, less extreme than in the 

 heterosporous Lycopods or Rhizocarps. 



We saw, in the case of C. Binneyana, that some of 

 the spores were abortive, and this is a point of some 

 importance, because we know that a similar process of 



SP 



Fig. 23. — Calamostachys Casheana. Tangential section, showing four sporangia 

 grouped around their sporangiophore (sf). Three contain megaspores and one 

 microspores. X 30. Phil. Trans. W. and S. Will. Coll. 1587. 



abortion goes on in heterosporous, as well as in some 

 homosporous Cryptogams, at the present day. It is an 

 interesting fact that in the heterosporous C. Casheana 

 we also find this abortion of some of the spores, but it 

 is confined in this species to the megasporangia. It 

 seems then that in this genus we are able to trace how 

 heterospory originated. The facts suggest that in the 

 first instance a certain number of spores became abortive, 

 and so allowed of better nutrition for the remainder ; 



