73. CmiATOPHYLLACE^E. 74. CALLITRICFACEJE. 371 



Order LXXIIL CERATOPHYLLACE^E. 



Fl. monoecious. Perianth free, in many divisions. Antb. 12 

 20, sessile, 2-celled, 2-pointed ; cells again partially divided. 

 Perianth usually wanting. Ovary 1-celled. Seed 1, pendulous. 

 Embryo straight; cotyledons 4, alternately smaller. No sti- 

 pules. Only one genus. 



1. CERATOPHYL'LUM Linn. Hornwort. 



1. C. demer'sum (L.); segments of 1. linear -filiform, fr. wing- 

 less having a spine on each side near the base and tipped with 

 the curved subulate style. E. B. 947. L. 2 4 times forked, 

 dark green, segments of uppermost 1. broader and more rigid. 

 Sometimes the spines are wanting, the style is short, and the 

 surface rough with minute tubercles. Ponds and ditches, rare. 

 P. VI. VII. E. S. I. 



2. C. summer' sum (L.) ; segments of L setaceous, fr. destitute 

 of spines covered when ripe with cylindrical tubercles and tipped 

 with the short curved style. E. It. 679. L. pale green. Young 

 fr. smooth. Ponds and ditches. P. VI. VII. E. 



Order LXXIV. CALLITRICHACEJ2. 



Fl. mostly monoecious, solitary, minute, usually with 2 white 

 bracts, no perianth. Stam. 1. Filament long. Anth. reniform, 

 1-celled, opening transversely at the top. Perianth none. Ovary 

 1, 4-angled, 4-celled. Styles 2, subulate. Fr. dry, 4-celled, 4- 

 lobed ; separating into 4 1-seeded indehiscent carpels. Embryo 

 in axis of fleshy albumen. .Radicle superior, long. Cotyledons 

 short, terete. No stipules. Only one genus of aquatic plants. 



1. CALLIT'KICHE Linn. Water-Star wort. 



A L. narrowed at the base ; lower linear, submerged ; upper 

 floating, broad, often spathulate and forming a rosette. Fr. 

 of 4 lobes cohering in pairs. C. verna L. 



1. C. verndlis (Koch); fr. nearly sessile longer than broad, 

 lobes parallel bluntly keeled on the back convex on the sides, styles 

 erect deciduous, bracts straightish deciduous. E. B. 722. 

 R. v. 129. C. verna (L.) ed. viii. Floating 1. ovate-spathulate, 

 in a rosette, rarely wanting. Fr. small ; keels of each pair 

 of lobes converging. Ponds and slow streams. A. or P. IV. 

 IX. E. S. L 



