73. CERATOPHYLLACE^. — 74. CALLITRICHACEjE. 293 



Order LXXIII. CERATOPHYLLACE^. 



ri. monoecious. Perianth free, in many divisions. Antli. 12 

 — 20, sessile, 2-celle(i, 2-pointed ; cells again partially divided. — 

 Perigone none. Ovary 1 -celled. Seed 1, pendulous. Embryo 

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



1. Ceratophyllum Linn. Hornwort. 



1. C. demersum (L.); segments of 1. linear-filiform, fr. not 

 winged with 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. 

 —Ponds and ditches. P. VI. VII. 



2. C. submersum (L.) ; segments of 1. setaceous, fr. destitute 

 of spines covered with cylindrical tubercles and tipped with the 

 short curved style. — E. B. 679. — L. pale green. Young fr. 

 smooth. — Ponds and ditches. P. VI. VII. 



Order LXXIV. CALLITRICHACE^. 



Fl. mostly mon«eeious, solitary, minute, usually with 2 white 

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

 I -celled, opening transversely at the top. — Perigone none. Ovary 

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

 lobed ; separating into 4, 1 -seeded, indehiscent carpels. Em- 

 bryo in axis of fleshy albumen. Radicle superior, long. Coty- 

 ledons short, terete. — Only one genus. 



1. Callitriche Linn. Water Starwort. 



1. C. verna (L.) ; fr. nearly sessile, lobes parallel in pairs 

 bluntly keeled on the back, styles erect deciduous, braets falcate. 

 — E. B. 722. R. v. 129. — Lower 1. linear ; floating 1. ovate-spa- 

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

 pair of lobes converging. Bracts falling short of fruit. — Common 

 in stagnant and slowly running water. A. or P. IV. — IX. 



2. C. platycarpa (Kiitz.) ; fr. nearly sessile, lobes parallel in 

 pairs slightly winged on the back, styles erect in flower persistent 

 and reflexed closely with fruit, bracts falcate. — E. B. S. 2864. 

 R. V. 129. — Lower I. of st. and branches linear; floating 1. round- 

 obovate-spathulate, in a close rosette, often wanting. Fr. twice 

 as large as that of C. verna, pale when dry. — [|3. C. stagnalis 

 (Scop.) ; lobes of fr. more spreading, I. all round obovate-spa- 

 thulate.'] — Common, especially on mud. A. or P. V. — IX. 



3. C. pedimculata (DC.) ; fr. stalked or nearly sessile, lobes 



