_A_ Plant in flower. _B_ Flower (the third sepal has fallen off). _C_ Lower part of the flower cut lengthwise.] FAMILY 24. XYRIDACEAE Herbs. Leaves radical, linear. Flowers in spikes or heads with an involucre of imbricate bracts, hermaphrodite. Sepals 3, one much larger than the others and deciduous. Petals 3, united below into a tube. Fertile stamens 3, adnate to the petals; staminodes 3. Anthers opening by longitudinal slits. Ovary superior, 1-celled or incompletely 3-celled. Ovules numerous, straight. Style 3-cleft. Fruit capsular. Embryo at the apex of the mealy albumen. (Plate 14.) Genus 1, species 40. Tropical and South Africa. Some are used in medicine. =Xyris= L. FAMILY 25. ERIOCAULACEAE Herbs. Leaves radical, linear. Flowers in heads surrounded by an involucre, very small, monoecious. Perianth membranous, simple or double, rarely in the female flowers none. Stamens 2-6. Anthers 2-celled. Ovary superior, 2-3-celled, with one pendulous ovule in each cell. Styles or style-branches 2-3. Fruit capsular. Embryo small, at the apex of the albumen.--Genera 4, species 80. Tropical and South Africa. (Plate 15.) 1. Stamens 2-3, opposite the petals. Petals of the male flowers united below, without a gland on the inside. Style-branches 6, three of which bear a stigma, rarely 3. [Subfamily =PAEPALANTHOIDEAE=.] 2 Stamens 4-6, very rarely fewer, but then petals free. Petals usually with a gland on the inside near the apex. Style-branches 2-3, without alternating appendages. [Subfamily =ERIOCAULOIDEAE=.] 3 2. Petals of the female flowers united at their middle part.--Species 6. Central and South Africa. (Under _Paepalanthus_ Mart.) =Syngonanthus= Ruhl. Petals of the female flowers free.--Species 3. West Africa and Mascarene Islands. =Paepalanthus= Mart. 3. Petals united into a tube, but free at the base in the female flowers. Inner involucral bracts more or less spreading. Stamens 6.--Species 8. Tropics. Some are used in medicine. (Plate 15.) =Mesanthemum= Koern. Petals free or absent. Inner involucral bracts rarely spreading.--Species 60. Tropical and South Africa. =Eriocaulon= L. SUBORDER BROMELIINEAE FAMILY 26. RAPATEACEAE Herbs. Leaves radical, lanceolate. Flowers in heads with 2 large involucral bracts, regular, hermaphrodite. Perianth corolla-like, yellow or whitish, 6-lobed. Stamens 6, inserted in the tube of the perianth. Anthers linear, opening by two terminal pores. Ovary superior, 3-celled, with 1 ascending, inverted ovule in each cell. Style simple. Fruit capsular. Embryo near the apex of the mealy albumen. Genus 1, species 1. West Africa (Liberia). =Maschalocephalus= Gilg & Schum. FAMILY 27. BROMELIACEAE