COMMELINACEAE. 67 



Order XYRIDALES. 



Terrestrial, commonly bog herbs, or epiphytes. Leaves often basal: 

 blades prevailingly narrow. Inflorescence usually not a spadix, but often 

 with a spathe-like bract or a spathe. Flowers mostly complete. Corolla 

 regular or nearly so (except in some genera of Commelinaceae and 

 Pontederiaceae). Gynoecium compound, superior or rarely inferior. 

 Fruit a capsule or utricle, or baccate. Seed with mealy endosperm. 



Inflorescence without a spathe : ovary 1-celled, with parietal placentae. 



Fam. 1. XTEIDACEAE. 



Inflorescence with a spathe : ovary mostly 3-celled. 

 Calyx and corolla of very different members : sta- 

 mens free. Fam. 2. COMMELINACEAE. 

 Calyx and corolla of quite similar members and 

 partially united : stamens partially adnate to the 

 perianth. Fam. 3. PONTEDERIACEAE. 



FAMILY 1. XYRIDACEAE. YELLOW-EYED GRASS FAMILY. 



Leaves basal : blades thickish. Flowers perfect, in a compact termi- 

 nal spike. Sepals 3, the two lateral firm, keeled and often appendaged, 

 persistent, the third larger, deciduous. Petals 3, fugacious. Androecium 

 of 3 stamens usually alternating with 3 staminodia: anthers linear. 

 Gynoecium 3-carpellary. Fruit a capsule. 



1. XYBIS [Gronov.] L. Eigid herbs of bogs, swamps, and pinelands. 

 Leaves not forked at the tip, imbricate at the base of the scape. Flowers 

 aggregated in a spike with closely imbricate scale-like bracts. Corolla yellow 

 or white. Anthers narrow, the sacs opening lengthwise. Sum. YELLOW- 

 EYED GRASS. 



Lateral sepals wingless, ciliate. 1. X. flexuosa. 



Lateral sepals winged, the wing incised or eroded above the 



middle. 2. X. caroliniana. 



1. X. flexuosa Muhl. Leaves narrowly linear, 5-30 cm. long, acute, straight 

 or spirally twisted: scapes 26 dm. tall, more or less spirally twisted, nearly 

 terete below, 2-edged above, smooth: spikes oval or subglobose, 5-10 mm. long: 

 lateral sepals margined, 4-5 mm. long; keel ciliate and bearded at the apex. 

 S. Frequent in swamps. Serpentine. 



2. X. caroliniana Walt. Leaves linear, attenuate, smooth, the longer fully 

 \ as long as the scape: scapes 1-6 dm. tall, flattened and 2 edged above, the 

 edges smooth: spikes oval or ovoid, 6-9 mm. long, obtuse; bracts loosely imbri- 

 cate in few series and splitting in age: lateral sepals 45 mm. long: wing 

 narrower than the sepal-body incised-toothed or eroded beyond the middle. 

 S. Rare, in swamps. Schists. 



FAMILY 2. COMMELINACEAE. SPIDERWORT FAMILY. 



Annual, or ours perennial, caulescent, succulent herbs. Leaves alter- 

 nate, sheathing at the base. Flowers perfect, the mostly umbel-like cymes 

 involucrate. Calyx of 3 persistent herbaceous sepals. Corolla of 3 equal 

 or unequal delicate petals. Androecium of 5-6 stamens, sometimes 2 or 



3. mere staminodia. Gynoecium 2- or 3-carpellary. Styles united. Fruit 

 a loculicidal 2- or 3-valved capsule. 



Petals alike in shape : polliniferous stamens 6, or rarely 5. 1. TRADESCANTIA. 



Petals unequal in size and shape : polliniferous stamens 3, or 



rarely 2. 2. COMMELINA. 



