498 Bicknell : Ferns and flowering plants of Nantucket 



come 7-10 mm. long and the perigynia 4-4.5 mm. A reduced 

 fresh-water form has heads sometimes not over 5 mm. long and 

 perigynia only 2-2. 5 "mm. in length. 



This is doubtless the C. adusta of Mrs. Owen's catalogue and 

 probably also the C. straminea var. alata. 



