370 94. LBMNACE^. — 95. POTAMOGETOSACE^. 



(cells bilocularp). Fronds with roots beneath. — Increasing 

 chiefly by buds. 



2. WoLFFiA. Spath 0. Fl. from upper surface of frond. 

 Stam. 1; aath. 1-celled, sessile. Frond very minute, 

 , rootless. — Increasing by buds from a lateral cleft. 



1. Lbmna Linn. Duckweed. 



1. L. trisul'ca (L.) ; fronds thin pellucid elliptic-fenceo/afe 

 tailed at one end sen-ate at the other, roots solitary. — E. B. 

 926. R. vii. 15. — Fronds half an inch long, proliferous at right 

 angles. Plants submerged, truly annual, producing buds which 

 survive the winter as in the other species. — Stagnant water. 

 A^ VI. E. S. L 



2. L. minor (L.) ; fronds ohoroate compressed opaque, roots 

 solitary blunt.— ^. £. 1095. H. vii. 14.— Fronds 1—2 lines 

 long, nearly flat beneath, of a compact texture. — On stagnant 

 water. A. VI. VII. E. S. I. 



•3. L. gib'ba (L.) ; fronds obovate nearly flat above hemispheri- 

 cal and spongy beneath, roots solitary blunt. — E. B. 1233. R. 

 vii. 14. Telmatophace Schleid., EndL — Fronds 1 — ^2 lines long, 

 at first flattish, afterwards remarkably gibbous and cellular 

 beneath. — On stagnant water. A. VI. — VlII. E. S. L 



4. L. polyrrhiza (L.) ; fronds roundish-obovate, compressed, 

 roots many clustered acute. — E. B. 2458. i?. vii. 15. Spirodela 

 Schleid., Endl. — Fronds half an in. long, green above, purple 

 beneath. Fl. have not been seen in Britain. — On water. A. 



E. S. I. 



2. WoLFPiA HorJcel. 



1. W. arrhiza (Wimm.) ; fronds very small subfflobular AMiah 

 above cellular beneath, solitary, young frond separating imme- 

 diately from the old one.—Sij. E. B. 1398. . B. vii. 14.— Frond 

 like a grain of sand, subglobular at all ages, green. Bud from 

 within the base of the old fr-ond. — Ponds near London. A. E. 



Order XCV. POTAMOGETONACE.^. 



Fl. perfect or imperfect. Perianth inferior, 4-parted, or 0. 

 Stam. free, 1, 2 or 4. Ovaries 4, distinct, each with 1 ovule 

 and 1 sessile stigma. Fr. a drupe enclosing a hard nut, or a 

 dry nut, not bursting, 1-seeded. Albumen 0. Embryo with a 

 thin skin having a lateral cleft. 



