FLORA OF THE DISTRICT OF COLUMBIA. 43 



Perianth present, sometimes small and scalelike. 

 Divisions of perianth small and scalelike, often shorter than the ovary, free from the 

 ovary (see also Dioscoreaceae). 



Leaves petioled, the blades broad and net- veined ARACEAE (p. 113). 



Leaves not petioled, linear, 

 Flowers in a single whitish involucrate head....ERIOCATJLACEAE (p. 115). 

 Flowers cymose or in heads, the latter not involucrate. 

 Flowers unisexual, in dense heads, the plants monoecious; perianth of a few 



obtuse scales, shorter than the fruit SPARGANIACEAE (p. 62). 



Flowers perfect; perianth of 6 greenish or brownish divisions. 



JTJNCACEAE (p. 117). 

 Divisions of perianth more or leas petal-like, colored or sometimes greenish. 

 Pistils several or many in a head or ring. Perianth of 3 outer green sepals and 



3 inner white petals; marsh herbs ALISMACEAE (p. 64). 



Pistil one, the cells or placentsc usually 3. 

 Perianth free from the ovary. 

 Stamens 3. 

 Flowers in a long-peduncled ovoid head; petals yellow; erect marsh or 



bog plantB with long narrow basal leaves XYRIDACEAE (p. 115). 



Flowers few from a short-peduncled spathe; petals yellow, blue, or white; 

 low creeping aquatic plants with scattered leaves. 



Heteranthera (p. 116). 

 Stamens 6 (rarely 4). 

 Perianth of 3 herbaceous or greenish sepals and 3 colored petals. ^ 

 Leaves in a whorl of 3 below the flower; petals withering only with age. 



Trillium (p. 124). 

 Leaves more than 3, not in whorls; petals delicate, quickly withering. 



COMMELINACEAE (p. 115). 



Perianth of 6 divisions, these similar in color, sometimes irregular in shape. 



Stamens dissimilar, 3 much longer than the other 3. Aquatic herbs 



with cordate petioled leaves and purplish flowers in dense spikes. 



Pontederia (p. 116). 



Stamens similar. 

 Plants climbing by tendrils. Fruit a berry. SMILACACEAE (p. 124). 

 Plants without tendrils. 

 Fruit a berry; basal leaves wanting. Root stocks present. 



CONVALLARIACEAE (p. 123). 

 Fruit a capsule; basal leaves usually present. 

 Styles 3 (united below in Uvularia); bulbs and corme usually 



wanting MELANTHIACEAE (p. 119). 



Style 1; bulbs or corms usually present.. LILIACEAE (p. 120). 

 Perianth adnate to the ovary. 

 Flowers irregular; stamens 1 or 2; ovules very numerous. 



ORCHIDACEAE (p. 127). 



Flowers regular; stamens 3-6; ovules few or numerous. 



Plants aquatic, submerged VALLISNERIACEAE (p. 66). 



Plants terrestrial, sometimes growing in marshes. 



Stems twining; leaves cordate DIOSCOREACEAE (p. 125). 



Stems not twining; leaves linear. 



Stamens 6; leaves not equitant; outer perianth divisions greenish 



below AMARYLLIDACEAE (p. 125). 



Stamens 3; leaves equitant; perianth divisions similar. 



IRIDACEAE(p.l26) 



