73. CERATOPHTLLACEiE. 74. CALLITHICHACE^. 303 



Order LXXTII. CERATOPHTLLACE^. 



Fl. monoecious. Perianth free, in many diTisions. Anth. 12 

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

 Perianth none. Ovary I-ceUed. Seed 1, pendulous. Embryo 

 straight ; cotyledons 4, alternately smaller. — Only one genus. 



1. Cebatophu'lttm Linn. Hornwort; 



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

 less having a spine on each side ntear ,the base and tipped -with 

 the curved subulate style. — L. 2 — 4 times forked, darlt green ; 

 segments of uppermost 1. broader and more rigid.— Ponds and 

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



2. C. mhmer'sum (L.) ; segments of I, setaceoiis, &. destitute 

 of spines covered when ripe with cylindrical tubercles and tipped 

 with the short curved style. — L. pale green. Young fr. smooth. 

 —Ponds and ditches. P. VI. VII. E. 



Order LXXIV. CAXLITEICHACE^. 



El. mostly moncBcious, solitary, minute, usually with 2 white 

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

 l-ceUed,openingtransversely atthetop. — Perianth none. Ovary 

 1, 4-anglecl, 4-ceiled. Styles 2, subulate. Fr. dry, 4-celled, 4- 

 lobed ; separating into 4 1-seeded in4phiseent carpels^ Embryo 

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

 short, terete. — Only one genus of aquatic plants. 



1. Cat.t.ti'eiche Linn. Water Starwort. 



1. C. ver'na (L.) ; fr. nearly sessile longer than broad, kibes 

 parallel and cohering in pairs bluntly keeled on the back convex on 

 the sides, styles erect deciduous, bracts straightish decidiious. — 

 jK. v. 129.-^Lower 1. linear^ floating 1. ovate-spathulate, in a 

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

 converging. — Common in ponds ai*d slow streams. A. or P. 

 IV,— IX. E. S. I. 



[C obtusan'gula (Le G.) ; fr. nearly sessile, lobes nearly sepa- 

 rated with rounded angles parallel in pairs, styles erect or spread- 

 ing persistent. To be looked for.] 



2. C. platycar'pa (Kiitz.) ; fr. nearly sessile, hbes parallel and 

 cohering in pairs slightly ivinged on the bach, styles erect in flower 

 persistent and reflexed closely with ifruit, bracts falcate persis- 

 tent. — K B. S. 2864. H. v. 129. — Lower I. of st. and branches 

 linear; floating. 1. round-obovate-spathulate, in a close rosette, 



