310 72. ETJTHOEBIACE^. 74. CALLITEICHAOEa;. 



stony and rocky woods, where it appears for 2 or 3 years after 

 tte bushes have been cut. Also naturalized on cultivated 

 ground. B. VI. VII. Caper-Spurge. E. 



3. Mbecttkia'lis Linn. Mercury. 



1. M. perm'nis (L.) ; st. simple, 1. stalked oblong-lanceolate 

 rough, female fl. on long common stalks, creeping. — B. B. 

 1873. — St. a foot high, usually naked below. Fl. m lax spikes. 

 — /3. M. ovata (Steud.) ; 1. nearly sessile ovate. — Woods and 

 thickets. B. Hm'stpierpoint, Suss. Mr. Mitten. P. IV. V. 



E. S. I. 



2. M. an'rma (L.) ; st. branched, 1. stalked ovate or ovate-ob- 

 long smooth, female ii. nearly sessile, root fibrous. — E.B.569. — 

 Height 6 — 12 iu. Bright green. Much branched. — fi. M. am- 

 bigua (L.) ; 1. lanceolate, fl. wliorled male and female intermixed. 

 E. B. S. 2816.— Waste and cultivated land. A. VIII. IX. 



E. S. I. 



Order LXXIII. CEEATOPHYLLACE^. 



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

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

 Perianth none. Ovary 1-oelled. Seed 1, pendulous. Embryo 

 straight ; cotyledons 4, alternately smaller. — No stipules. — Only 

 one genus. 



1. Ceeatophtl'ltjm Linn. Hornwort. 



1. C. demer'sum (L.) ; segments of I. 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. — 

 Ponds and ditches, rare. P. VI. VII. E. S. I. 



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

 of spines covered when ripe with cylindrical tubercles and tipped 

 with the short curved style. — E. B. 679. — L. pale green. Yoimg 

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



Order LXXIV. CALLITEICHACEvE. 



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

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

 l-ceUed, opening transversely at the top. — Perianth none. Ovary 

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

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

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

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



