THE GENUS EQUISETUM 



and litorale, having smaller chromosomes than members of the other subgenus, which, 

 in this study, have been represented by E. variegatum, hiemale, scirpoides, ramosissi- 





w 



% «^% m^ ?. '•^ 



« « 



■IT / * 





Fig. 215. Permanent acetocarmine preparations of two additional large-chromosomed species of 

 horsetail, x 1000. In both 7; = almost certainly 108. a. Equisetum hiemaleh.hom Northumberland, 

 the first meiotic metaphase. For explanatory diagram see Fig. 216. b. E. scirpoides Michx., the 

 second meiotic anaphase to show shapes of the chromosomes at this stage. 



mum, robustum, trachyodon and Moorei. Though the subgenera are primarily distinguished 

 by the structure of their stomata, the agreement between this character and relative 

 chromosome size suggests that the subdivision is a natural one and of long standing. 



218 



