Peteridophytes 



149 



There are also a few hypnums found intermixed with 

 sphagnum on the surface of bogs, and as everyone 

 knows there are hosts of mosses in aU moist places in 

 woods and by watersides. 



Fig. 61. Two floating leaves of the "water shamrock,' 

 of a surface layer of duck-meat (Spirodela polyrhiza). 



Marsilea, in the midst 

 "Lemna" on fig. 62. 



Pteridophytes — Aquatic fernworts are few and of very 

 unusual types. There is at least one of them, how- 

 ever, that is locally dominant in our flora. Marsilea, 

 the so-called water shamrock or water fern, abounds on 



