Aquatic or marsh herbs, with milky juice. Leaves with axillary scales. Flowers regular. Perianth of 3 sepals and 3 petals, rarely in the female flowers of 3 sepals only. Stamens 6 or more, rarely 3. Anthers opening outwards. Pollen-grains globular. Carpels 6 or more, rarely 3, distinct or united at the base. Ovules solitary in each carpel, rarely two or more, inverted. Seeds without albumen; embryo curved.--Genera 9, species 15. Tropical and North Africa. (Plate 6.) 1. Carpels on a large and distinctly convex receptacle. Inner perianth-segments petal-like, larger than, or almost as large as the outer. Stamens 6 or more. [Tribe SAGITTARIEAE.] 2 Carpels on a small and almost flat receptacle. 4 2. Flowers hermaphrodite. Ripe carpels numerous, slightly compressed, with many ribs.--Species 3. Central and North-west Africa. (Under _Alisma_ L.) =Echinodorus= Engelm. Flowers unisexual or polygamous. Ripe carpels much compressed laterally. 3 3. Flowers monoecious or polygamous. Petals a little longer than the sepals. Carpels many. Ripe carpels with two crest-like ribs.--Species 1. Tropics. (_Lophiocarpus_ Miq., under _Sagittaria_ L.) =Lophotocarpus= Th. Dur. Flowers dioecious. Petals shorter than the sepals, white. Carpels 7-9. Ripe carpels with 3 ribs.--Species 1. German South-west Africa. =Rautanenia= Buchenau 4. Petals much smaller than the sepals or wanting. Stamens 3 or 9. [Tribe WIESNEREAE.] 5 Petals larger than the sepals, coloured. Stamens 6, rarely 9. [Tribe ALISMEAE.] 6 5. Flowers dioecious. Petals in the female flowers wanting. Stamens 9. Carpels about 12.--Species 1. East Africa. =Burnatia= Mich. Flowers monoecious. Petals present, but very small and falling off early. Stamens 3. Carpels 3-6.--Species 2. East Africa and Madagascar. (_Wisneria_ Mich.) =Wiesnera= Mich. 6. Carpels 6-8, united at the base and spreading horizontally, containing 2 or more ovules each and opening by a lid when ripe.--Species 2. North Africa. The root-stock is edible. =Damasonium= Tourn. Carpels 6-20, distinct, with a single ovule in each, indehiscent. 7 7. Flowers polygamous-monoecious. Carpels 15-20. Pericarp bony within, hollow on either side. Leaves sagittate.--Species 3. Tropics. (Plate 6.) =Limnophyton= Miq. Flowers hermaphrodite. Leaves ovate, cordate, or lanceolate. 8 8. Carpels 6-12, irregularly whorled, slightly compressed and 3-5-ribbed when ripe; pericarp woody within.--Species 2. Tropics and Egypt. (Under _Alisma_ L.) =Caldesia= Parl. Carpels 15-20, distinctly whorled, much compressed and 2-ribbed when ripe; pericarp leathery or parchment-like.--Species 1. North and East Africa. The root-stock contains starch and is used in medicine. “Water-plantain.” =Alisma= L. SUBORDER BUTOMINEAE FAMILY 13. BUTOMACEAE