CERATOPHYLLE.E. 105 



ORDER 163. PODOSTEME^. 



Only one species is found in North America ; a few are found 

 in South America, and the African Islands. Herbs with floating 

 stems, and capillary or linear leaves irregularly divided, or minute 

 and imbricated. Flowers small, naked, bursting through a spathe, 

 monoecious, without calix or corolla. 



PODOSTEMUM. L. 19. 2. 



P. ceratophyllum. Mx. Threadfoot. Grows on rocks in 

 streams, with a filiform stem, and floating with its pinnate leaves 

 and axillary flowers ; blossoms in July ; near Amherst. 



ORDER 164. CALLITRICHINEiE. 



One genus and 3 species make up this order in North America, 

 and 2 of the 3 species are in Massachusetts. The relations of 

 plants of this order are little understood. 



Callitriche. L. 1. 2. Water-Star. 



C. verna. Muhl. Named from the Greek, beautiful hair. 



It is a small plant. Stem floating, filiform, with small, lanceolate, 



opposite leaves, spatulate, and obovate, forming star-like tufts at 



the end of the stems ; fresh water ; blossoms in May to August. 



C. linearis, Ph. Seems to be C. autumnalis, L., and differs 

 little from the preceding, except in its more linear leaves ; grows 

 in the same situations. 



ORDER 165. CERATOPHYLLEiE. 



Only 1 genus and 2 species known in North America. Like 

 the preceding order, the relations are scarcely made out, and the 

 orders become isolated genera. 



Ceratophyllum. L. 19. 12. 



C. demersum. L. Hornwort. The name means horn-leaf, 

 14 



