152. DIOSCOREACEJi. [1. Dioscorea. 



base amplexicaul and sheathing, often with white gUstening scales 

 and margins very frequently prickly. Inflorescence generally from 

 the centre of the rosette, terminal, sessile or peduncled in spikes, 

 racemes, or panicles often densely aggregated in heads, and frequently 

 with brilliantly coloured bracts on the axis below the flowers and 

 passing into the proper bracts of the flowers, sometimes also a crown 

 of bracts or foliage leaves (as in the Pine-apple) terminates the axis. 

 Flowers 2-sexual, usually regular. Perianth separable into 3-merous 

 calyx and corolla, calyx persistent herbaceous or coriaceous, sepals 

 free or connate, petals free or united into a tube below or entirely 

 connate, frequent!}^ Avith 2 scales at the base within. Stamens 6, free 

 or connate or one whorl free, the other connate, anthers introrse. 

 Ovary inferior, half inferior or superior, if superior then sessile by a 

 very broad base, 3-celled, style with 3 stigmas or stigmatose branches. 

 Ovules in each cell indefinite, usually very many, anatropous. Fruit 

 baccate, sometimes combined below into a syncarp, and often crowned 

 by the calyx, sometimes dehiscent. Embryo small, at the lower end 

 of the seed near the hilum in a small pocket or fork of the mealy 

 albumen. 



Tlie family is exclusively tropical and sub-tropical American, but several 

 beautiful plants of the family are common in India in grass conservatories, veran- 

 dahs, etc., a few like Pitcairnia with long leaves white scaly on the undersurface 

 are large plants and grow in the open. 



Ananas sativus, Livdl., is the Pine-apple, which is largely groA\Ti and is serai- 

 naturalized in some of the warmer moister districts. There are also ornamental- 

 leaved pineapples in gardens. 



FAM. 152. DIOSCOREACE^. 



Climbing, very rarely erect, herbs or suffruticose, usually from a 

 tuberous rootstock or hard rhizome Avith fleshy and tuberous roots. 

 Leaves opposite or alternate entire lobed or digitately 3-5-foliolate, 

 palminerved and with reticulate venation between ; petiole often angular 

 and twisted at the base. Flowers regular, small or minute, usually 

 dioecious, rarely hermaphrodite, spicate, racemed or panicled. 

 Perianth usually shortly tubular below, tepals 2-seriate, male and 

 female sub-similar. Alale with stamens inserted at the base of the 

 perianth or on the lobes, 3 or 6 or 3 perfect and 3 staminodes, anthers 

 small, pistillode sometimes present. Female with 3, 6 or staminodes, 

 ovary inferior, 3-quetrous and 3-cellecl (in our genera), styles 3 very 

 short or stigmas sub-sessile entire or 2-fid, recurved. Ovules 2 super- 

 posed in each cell, pendulous, anatropous or subamphitropous. 

 Fruit a 3-valved capsule or baccate. Seeds flat or globose with small 

 embryo included in hard albumen. 



1. DIOSCOREA, L. Yam. 



Our only genus. Fls. 1 -sexual, usually dioecious. Capsule coria- 

 ceous, 3-winged with 2 flattened or winged seeds in each cell. 



Although the wild Yams are of great importance as food to the forest tribes, 

 very little rehance can usually be placed on the vernacular names, and I have 

 heard the male and female plant of the same species called by dirterent names by 

 the same man. In general the deeper rooted yams are the most esculent and 

 considerable labour is involved in digging up the tubers. 



1115 



