FAMILIES OF FLOWERING PLANTS. 57 
Family Taccaceae. Tacca Family. The type and only important 
genus of this small family furnishes the pia plant, (Zacca pinuatifida) 
an herb extensively cultivated throughout the East Indies and Poly- 
nesia as a source of arrowroot. The plauts of the family are all 
tropical herbs, with thick roots and basal leaves, the flowers usually 
small, and borne in umbellate clusters. 
Fic. 49.—The wild yam, Dioscorea villosa, showing flowers and fruit. Original, 
Family Dioscoreaceae. Yam family. Contains about 9 genera 
and nearly 200 species, chiefly natives of tropical America. They are 
herbaceous or woody twining vines, the leaves mostly alternate and 
netted-veined, the flowers dioecious or monoecious, small and incon- 
spicuous, in axillary clusters. The fruit in Dioscorea, the type genus 
