13. BUTOMACEAE — I4. HYDROCIIARITACEAE ']■] 



SUBORDER BUTOMINEAE 



FAMILY 13. BUTOMACEAE 



Aquatic or marsh lierbs. Leaves linear or lanceolate. Flowers in umbel- 

 like cymes, regular, hermaphrodite. Perianth of 6 segments, all, or the inner 

 ones only, petal-like. Stamens g, very rarely fewer. Pollen-grains globular. 

 Carpels 6, very rarely fewer, distinct or united at the base only, opening when 

 ripe along the ventral suture. Ovules on irregularly branched parietal placen- 

 tas, numerous, inverted. Seeds without albumen. — Genera 2, species 2. North 

 and Central Africa. (Under ALISMACEAE.) 



Perianth-segments nearly equal, all petal-like, pink, persistent. Embryo 

 straight. Leaves linear. Juice not milky. — Species i. North-west 

 Africa (Algeria). Used as a garden plant. The root-stock is edible. 

 " Flowering-rush." Butomus Tourn. 



Perianth-segments unequal, outer sepal-like, inner petal-like, white, falling 

 off very early. Embryo horseshoe-shaped. Leaves eUiptical. Juice 

 milky. — Species i. Northern part of Central Africa. {Buiomopsis 

 Kunth) Tenagocharis Höchst. 



FAMILY 14. HYDROCHARITACEAE 



Aquatic herbs. Leaves with axillary scales. Flowers enclosed when young 

 in a one- or several-flowered spathe of one or two bracts, regular, rarely some- 

 what irregular. Perianth consisting of a calyx and a corolla, rarely simple. 

 Stamens 2 — 12. Anthers opening outwards or laterally. Ovary inferior, 

 more or less distinctly one-celled, with 2 — 15 parietal placentas, which some- 

 times form incomplete dissepiments. Seeds without albumen. — Genera 10, 

 species 40. (Plate 7.) 



1. Stigmas 2 — -5. Placentas as many, slightly raised 2 



Stigmas 6 or more. Placentas as many, much projecting and generally 



meeting in the centre of the ovary 6 



2. Petals none. Stamens 3. Pollen-grains fiUform. Stigmas several times 



as long as the sepals. Embryo with a strongly developed radicle. 

 Totally submerged marine plants. Leaves more or less distinctly 

 stalked. — Species 2. Indian Ocean. [Subfamily HALOPHILOIDEAE.] 



Halophila Thouars 

 Petals present, but sometimes very small and falling off very early. Pollen- 

 grains globular. Stigmas at most twice as long as the sepals. Embryo 

 with a not very strongly developed radicle. Freshwater plants ; flowers 

 raised above the water. Leaves sessile. [Subfamily VALLISNERIOI- 

 DEAE.] 3 



3. Leaves whorled. Spathes i-flowered. Flowers unisexual. Stamens 3. — • 



Species i. Upper Nile, Madagascar, Mauritius. Used in refining 



sugar. [Tribe HYDRILLEAE.] .... Hydrilla L. C. Rich. 



Leaves spirally arranged. Spathes of the male flowers several-flowered. 4 



