140 37- DIOSCOREACEAE — 38. IRIDACEAE 



FAMILY 37. DIOSCOREACEAE 



Root-stock tuberous. Stem twining. Leaves alternate, net-veined, usually 

 cordate. Flowers in racemes, inconspicuous, regular, unisexual. Stamens 6. 

 Ovary inferior, 3-celled. Ovules 2 in each cell, superposed, inverted. Styles 

 or style-branches 3. Embryo enclosed in a horny or cartilaginous albumen. — 

 Genera 2, species 45. (Plate 21.) 



Fruit a berry. Seeds not winged. — Species 3. North Africa. The tubers 

 are eaten and used in medicine; the berries are poisonous. [Tamnns 



Juss.) Tamus L. 



Fruit a capsule. Seeds winged. — Species 40. Tropical and South Africa. 

 Some are cultivated for their edible tubers (yams) or used in medicine ; 

 others are poisonous. (Including TesUidinaria Salisb.) (Plate 21.) 



Dioscorea I^. 

 SUBORDER IRIDINEAE 



FAMILY 38. IRIDACEAE 



Herbs or undershrubs. Inflorescence terminal. Flowers hermaphrodite. 

 Perianth with 6 petaloid segments. Stamens 3, inserted opposite the outer 

 perianth-segments. Anthers turned outwards. Ovary inferior, 3-celled, 

 rarely {Hermodactyhis) i-celled. Style-branches usually divided or dilated. 

 Ovules numerous, inverted. Fruit a loculicidal capsule. Embryo enclosed 

 by the horny albumen. — Genera 39, species 600. (Plate 22.) 



1. Flowers solitary, terminal, sometimes surrounded by several axillary 



flowers, each flower with a spathe. Perianth regular ; inner and outer 

 segments nearly equal. Leaves not exactly 2-ranked. Stem short 



or almost wanting. [Subfamily CROCOIDEAE.] 2 



Flowers in various inflorescences, rarely spathes solitary, but 2- or more- 

 flowered or (if i-flowered) the outer perianth-segments very different from 

 the inner ones. Leaves 2-ranked, folded one above the other, rarely 

 (Geosiris) reduced to scales. Stem distinctly developed. ... 5 



2. Stem underground, very short. Perianth-tube very long. ... 3 

 Stem partly above ground. Perianth-tube short or moderately long. 4 



3. Style-branches undivided, stigmatose inside. Perianth red or violet, 



rarely white with red streaks. — Species 6. South Africa (Cape Colony). 



Syringodea Hook. fil. 

 Style-branches many-lobed or many-parted, stigmatose at the top. — 

 Species 3 ; one of them only cultivated. North-West Africa. Used 

 as ornamental plants ; the tubers are edible. The cultivated species 

 (C. sativus L.) yields the saffron, which is used as a condiment and for 

 dyeing Crocus L. 



4. Leaves crowded at the top of the very short stem. Perianth with a rather 



long tube, yellow or violet. Filaments united into a tube. Style- 

 branches dilated above, petal-like. — Species 3. South Africa (Cape 

 Colony). Used as ornamental plants Galaxia Thunb. 



