328 CERATOPHYLLACE^E. (HORNWOBT FAMILY.) 



Order 71. CALXITRICHACE^. (Water- St arworts.) 



Small slender aquatic herbs, with opposite entire leaves, no stipules 

 and monoecious axillary flowers without perianth, but sometimes with 

 2 bracts j stamen 1, with slender filament and heart-shaped 4-celled 

 anther; ovary 4-celled, with 2 styles; fruit 4-lobed, flattened and 

 emarginate. Flowers mostly solitary, sometimes a male and female in 

 the same axil 



1. CALLITRICHE, L. 



Characters given under the order. 



1. C. verna, L. Amphibious, with elongated stems and floating rosulate 

 obovate often emarginate leaves, the submerged ones from spatulate to linear: bracts 

 often exceeding the fruit, rarely wanting : styles erect or spreading, deciduous : 

 fruit orbicular or obcordate or elliptical, of connate carpels. — From California 

 and Oregon to Montana and Wyoming, and eastward across the continent. 



2. C. autumnalis, L. Submersed, with numerous uniform linear one-nerved 

 leaves, truncate or refuse at the apex: flowers ivithout bracts: styles reflex ed, 

 caducous : fruit round, deeply notched, the margins thin or at length winged. 

 — From California northward, and thence eastward across the continent. 



Order 72. ■ ERATOPHYIXACE JE. (Hornwort Family.) 



Aquatic herbs, with whorled finely dissected leaves, and minute axil- 

 lary and sessile monoecious flowers without floral envelopes, but with an 

 8 to 12-cleft involucre in place of a caly the fertile a simple 1 -celled 

 ovary. 



1. CEEATOPHYLLUM, L. 



Sterile flowers of 12 to 24 stamens, with sessile anthers. Fruit an ache- 

 nium, beaked with a slender persistent style. — Submersed plants, in ponds 

 or slow-flowing streams : the sessile leaves cut into thrice-forked threadlike 

 divisions. 



1. C. demersum, L. Stems very slender, a foot or two long: leaves 

 in numerous whorls of 6 to 8 : akene elliptical, shortly stipitate, with a short 

 spine or tubercle on each side near the base. — California and northward, 

 thence eastward across the continent. 



Order 73. URTICACE^. 



Plants generally with stipules, and monoecious or dioecious, or rarely 

 perfect flowers, furnished with a regular calyx, free from the 1 -celled 

 ovary which forms a 1-seeded fruit; stamens as many as the lobes of 

 the calyx and opposite them, or sometimes fewer. 



