CERATOPHYLLE^. 105 



ORDER 163. PODOSTEME.E. 



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 cahx 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. CERATOPHYLLE.E. 



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, 



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