478 FLORA OF TEXAS. 



CERATOPHYLLUM, L. Hori^wort. 



C. DEMERSUM, L. Leaves rigid, 6-9 in a whorl, once or 

 twice forking, with the lobes spiny-toothed ; achenium oval, 

 compressed, tubercular-roughened on the sides, and armed 

 near the base with 2 lateral widely-spreading slender spines. 

 In still water. September and October. /S'/e?7i5 l°-4° long ; 

 leaves near the end of the branches much crowded. 



109. STAKWORT FAMILY. Order, Callitrichace^. 



Small aquatic annuals, with opposite entire leaves, and 

 solitary axillary polygamous jlowers without floral envel- 

 opes ; stamen mostly solitary, 2-bracted in the sterile flower; 

 filament slender; anther reniform, the cells confluent; 

 styles 2, slender ; stigmas acute ; capsule 4-angled, 4-celled, 

 with a single suspended anatropous seed in each cell, inde- 

 hiscent; emlryo straight, in copious fleshy albumen ; radi- 

 cle long, superior. Consisting of the single genus 



CALLITRICHE, L. Water-Starwort. 



C. YERis"A, L. Leaves floating, obovate or spatnlate, 

 lower ones crowded. Fruit sessile, keeled on the back. 

 Stems several, 6'-12' long ; leaves ^' long. 



110. RIVER- WEED FAMILY. Order, PoDOSTEMACEiE. 



Moss-like aquatic plants, with minute flowers, from a 

 spatJie-like involucre, and destitute of floral envelopes; 

 stamens 5-12; anthers 2-celled; capsule 2-3-celled, and 

 pointed by as many persistent styles ; seeds numerous, on 

 a thick central placenta, destitute of albumen. 



