White Nile Prov. (14° 30′ L.N. & J. Nyemati); Fung Prov. 749 =Ottelia alismoides= _Pers._ Aquatic herb with very short stem. Leaves with long 3-angled pet., broadly cordate, 4-6 in. wide, 7-11 nerved Fl. hermaphr., solitary; ped. 6-12 in. long, at length spirally contracted; spathe 3-6 toothed and winged, adnate to ovary; outer per. segm. 3, oblong, ½ in. long, inner segm. 3 petaloid, white, 1 in. long; sta. 6-10; styles 6, bifid; ovary 6-celled. White Nile Prov. (Tawila); Kordofan Prov. =O. lancifolia= _A. Rich._ Leaves radical, lanceolate, tapering into the pet., which is subamplexicaul at the base. Spathe bifid; inner per. lobes yellow. White Nile Prov. (Tawila); Darfur Prov. (J. Marra, Middle Gindi basin, 4,900 ft.); Bahr El Ghazal Prov. The seeds are pounded into meal by Nuers, and eaten. =O. ulvæfolia= _Buch._ Leaves attenuate at both ends, 7-nerved, 1½ in. broad. Spathe winged, obtusely 6-angled; inner per. lobes bright yellow, 1 in. long. White Nile Prov. (Salati); Bahr El Jebel (Sudd). =O. near O. ulvæfolia= _Buch._ Submerged leaves narrowly linear-oblanceolate, up to 1 ft. long. Spathes 1¾ in. long, smooth. Flowers yellow. White Nile Prov. (Tawila). 750 =Boottia scabra= _Benth._ & _Hook. f._ Leaves submerged, thin, oblanceolate, 1½-2 ft. long, 2½ in. wide; petiole 1 ft. long, expanded at the base into an amplexicaul base. Spathe 3½ in. long, unisexual, rugose, toothed. Petals yellow or cream coloured. White Nile Prov.; Bahr El Ghazal Prov.; Bahr El Jebel (Sudd). =B. abyssinica= _Ridl._ As above, but spathe smooth, and only 2 in. long. Bahr El Ghazal Prov. (Jur Ghattas & Main River); Mongalla Prov. (Kagulu Khor, Yei River); Bahr El Jebel (Madi). 751 =Thalassia Hemprichii= _Ehrb._ Submerged marine plant. Leaves fascicled at intervals, linear, 6 in. long. Infl. diœcious; male spathes solitary, 2-leaved; per. 3-lobed; sta. 6. Fem. fl. at length stalked; ovary long-beaked. Fruit globose. Red Sea Prov. (Suakin & Arakea). 752 =Halophila ovata= _Gaud._ Submerged marine herb, just above low-water mark. Leaves 2 from each node, ovate, 1 in. long; pet. 1 in. long. Male fl. solitary; per. 3-lobed; sta. 3. Fem. fl. sessile in the spathe; per. segm. 3, minute; styles 3; ovary beaked. Red Sea Prov. (Suakin). =H. stipulacea= _Aschers._ Leaves linear, 2 in. long; pet. ¼ in. Much as above. Red Sea Prov. (Dongonab). =LEMNACEÆ.= 753 =Lemna polyrhiza= _Linn._ Duckweed, the floating front bearing several roots. Bahr El Ghazal Prov. (Meshra El Rek). It has been suggested that this plant might be utilised in anti-mosquito work, as pools covered with it never contain larvae of the Culicidae. =L. paucicostata= _Hegelmeier._ The floating frond nearly ⅓ in. long, bearing 1 root.