Lemna.] cli. lemnace^ (brown). 201 



1. LEMNA, Linn. ; Benth. et Hook. f. Gen. PI. iu. 1001. 



Flowers seated in a cavity at the margin of the frond, enclosed in a 

 minute membranous spathe, very minute, very rarely seen in some of 

 the species. Stamens 1-2 ; anthers 2-celled ; cells opening by trans- 

 verse slits. — Fronds small or minute, with one or more roots from their 

 under surface, floating on still waters, thin and flat, or flat above and 

 more or less convex beneath, suborbicular, elliptic, oblong, obovate or 

 spathulate in outline, entire, or in one species minutely denticulate on 

 the margin ; roots tipped with a distinct sheath-like root-cap. 



Species about 16. Widely distributed in all the warm and temperate parts of 

 both hemispheres. 



Each frond with several roots 1. L. poJyrhiza. 



Each fiond with one root only. 



Fronds subrotund, 1^-3 lin. in diam., underside very 



convex and greenish-white . . . . 2. L. gihha. 



Fronds elliptic or elliptic-oblong, |-2^ lin. long, 

 rather thin, flat above, not very convex beneath. 

 Eoot-cap obtuse ; root-sheath not winged . . 3. X. minor. 



Root-cap acute ; root-sheath winged . . . 4. X. paucicostata. 



Fronds elliptic, ^-§ lin. long, obtusely keeled above 5. L. cequinoctialis. 



1. Ij. polyrhiza, Li7in. Sp. PI. ed. i. 970. Fronds H-4 lin. long, 

 lJ-4 lin. broad, elliptic, suborbicular, or somewhat obovate, usually 

 slightly oblique at the basal end, thin, flat above, slightly convex 

 beneath, bright green above, purple beneath ; young fronds sessile. 

 Koots several, fascicled on the undersurface of each frond, towards the 

 basal end. Flowers very rarely seen. — L. 'polyrrhiza^ Engl. Bot. ed. 3, 

 ix. 23, t. 1897; Reichb. Ic. Fl. Germ. vii. 9, t. 15, fig. 17; Schweinf. 

 Beitr. Fl. Aethiop. 292. Spirodela polyrrhiza, Schleid. in Linnaea, xiii. 

 392; Kunth, Enum. iii. 7; Hegelmaier, Monogr. Lemn. 151, t. 13, 

 figs. 10-16, and t. 14-15, and in Engl. Jahrb. xxi. 284 ; Engl. & Prantl, 

 Pflanzenfam. ii. iii. 164 and 154, figs. 101, A, 102 ; Dui-and & Schinz, 

 Conspect. Fl. Afr. v. 485 ; Engl. Pfl. Ost-Afr. C. 422. 



X7pper Guinea. Lower Niger : Onitsa, Barter, 583 ! 



ITile l^and. British East Africa : Meshra, on the Ghazal River, Schweinfurthf 

 1281 ! Mpororo district, Stuhlmann (ex Hegelmaier). 



Widely distributed in most warm and temperate regions. 



2. Ij. gibba, Linn. Sp. PI. ed. i. 970. Fronds 1 J-3 lin. long, and 

 nearly as broad, subrotund or broadly obovate, very thick when alive, 

 flat and bright green above, very convex, greenish-white and somewhat 

 spongy beneath, young fronds sessile. Roots solitary from the under- 

 surface of each frond. Flowers rare. — Engl. Bot. ed. 3, ix. 22, t. 13!m; ; 

 Reichb. Ic. Fl. Germ. viii. 8, t. 14, fig. 16; Hegelmaier, Monogr. 

 Lemn. 145, t. 11-13, and in Engl. Jahrb. xxi. 289; Engl, k Prantl, 

 Pflanzenfam. ii. iii. 164,154, fig. 101,C, and 100, fig. 106, D; 1^11 in Journ. 

 Linn.Soc. xvi. 685; Durand & Schinz, Conspect. Fl. Afr. v. 484; Schwein- 

 furth in Bull. Herb. Boiss. ii. App. ii. 53, 105; N. E. Br. in Dyer, Fl. 



