56 STUDIES IN FOSSIL BOTANY 



•practically identical with the homosporous species C. 

 Binneyana, the differences between them being of a trivial 

 kind. In some of the sporangia, however, numerous 

 small spores are contained — slightly smaller than those 



c 



Fig. 22. — Calamostachys Binneyci7ia. A single sporangiumj containing spores in tetrads. 

 Many of the spores are abortive (£). The structure of the sporangial wall is well 

 shown. X ioo. A. Tetrad with all four spores about equal. B, C. Tetrads, each 

 with one abortive spore. D. Ripe spores showing the triradiate marks. A-D X 200. 

 Phil. Trans., W. and S. Will. Coll. 1011, etc. 



of C. Binneyana, while other sporangia on the same cone, 

 and sometimes on the same sporangiophore, contain 

 a much smaller number of large spores, the diameter of 

 which is just three times that of the former (see Fig. 23). 

 Here, therefore, we have a perfectly clear case of a 



