316 



where I have seen them ; but they are so minute as to require to be magnified 

 200 times to be distinctly observed. 



Geography. Of 20 species enumerated by writers, all are inhabitants of 

 ditches or inundated places, in various parts of the world. They do not appear 

 to be affected by climate so much as by situation, whence they have been de- 

 tected in various parts of Europe, Asia, Africa, and America ; chiefly, how- 

 ever, in temperate latitudes. 



Properties. Unknown. 



Examples. § 1. Marsileace^e, Ad. Brongn. in Diet. Class. 10. 196 

 (1826), Marsilea, Pilularia. 



§ 2. Salvinie^e, Id. 1, c, Salvinia, Azolla, 



