PONTEDERIACEAE 243 



10. Commelina elegans H.B.K. Stems erect or branching at the base ; branches de- 

 cumbent, rooting at the nodes, 2-8 dm. long, with short or elongated puberulent internodes : 

 leaf -blades lanceolate to elliptic or oblong-lanceolate, 4-10 cm. long, acute or acuminate, 

 some often rounded at the base ; sheaths 1-1.5 cm. long, naked or sparingly ciliate on the 

 spreading margin : spathes short-peduncled, glabrous, at least without long hairs at the base, 

 1.5-2 cm. long, acute : petals blue or white : capsules obovoid, 4 mm. long, reticulated 

 especially on the dorsal lobe : seeds 3, smooth. 



In sand, peninsular Florida and tropical America. Spring and fall. 



11. Commelina hirtella Vahl. Stems erect, ascending or reclining, 2-12 dm. tall, 

 somewhat pubescent, more or less branched : leaf-blades lanceolate or oblong-lanceolate, 

 10-20 cm. long, acuminate, often roughish, narrowed into short petiole-like bases ; sheaths 

 1-2.5 cm. long, fringed with brown hairs : peduncles very short : spathes usually clustered, 

 triangular or triangular-ovate, 2-2.5 cm. long, acute, united at the base, strongly nerved 

 and cross-nerved : capsules 7-8 mm. long, smooth and shining : seeds 5 in each capsule, 

 4-6 mm. long, granular-puberulent. 



In swamps and alluvial soil, New Jersey to Missouri, Florida and Texas. Summer and fall. 



FAMILY 5. PONTEDERIACEAE Dumort. PICKEREL-WEED FAMILY. 



Bog or aquatic herbs, with rootstocks. Leaves alternate, often clustered, 

 sometimes mainly basal : blades ribbon-like or much dilated. Flowers perfect, 

 more or less irregular, solitary or in spikes subtended by leaf-like spathes. Peri- 

 anth corolla-like : members 6, partially united. Androecium of 3-6 stamens 

 partially adnate to the perianth. Filaments filiform, or dilated at the base, or 

 thickened about the middle. Gynoecium a compound pistil. Ovary 3-celled 

 with axile placentae, or 1-celled by suppression. Stigma entire or minutely 

 toothed. Ovules solitary or numerous, anatropous. Fruit a 1-celled 1 -seeded 

 utricle, or a many-seeded capsule. Endosperm mealy, copious, surrounding the 

 central embryo. 



Stamens 3, or rarely 1-4. 1. HETERANTHERA. 

 Stamens 6. 



Ovary 1-oelled (by suppression): ovule and seed solitary : fruit indehiscent. 2. PONTEDERIA. 



Ovary 3-celled : oVules and seeds numerous : fruit 3-va'lved. 3. PIAROPUS, 



1. HETERANTHERA R. & P. 



Herbs, with creeping or floating stems. Leaves alternate : blades broadened, or 

 grass-like, often petioled, sometimes reduced to phyllodes. Spathes bract-like, 1-several- 

 flowered. Perianth white, blue or yellow : members equal or nearly so, narrow, or 

 dilated. Stamens 3, or rarely 1-4 : filaments often unequal : anthers erect, introrse. 

 Ovary 3-celled, sometimes incompletely so : style filiform. Ovules numerous, in 2 

 rows on each placenta. Capsule somewhat elongated, enclosed in the withered perianth. 

 Seeds numerous, ribbed. [Schollera Schreb. ] 



Leaves not differentiated into blade and petiole, linear : perianth yellow. 1. H. dubia. 

 Leaves differentiated into petiole and blade : perianth white or blue. 



Leaf-blades longer than broad : spathes 1-flowered. 2. H. liinosa. 



Leaf-blades broader than long : spathes 2-5-flowered. 3. H. rentformis. 



1. Heteranthera diibia (Jacq. ) MacM. Stems floating or creeping, 2-9 dm. long, 

 branched : leaves linear, more or less elongated, flat, acute, sheathing at the base : spadix 

 1-2-flowered : perianth light yellow, delicate ; tube about 1 mm. thick ; lobes linear, 8-12 

 mm. long : filaments dilated below : anthers linear-sagittate : seeds oblong or oval-ob- 

 long, 1.5 mm. long, delicately ribbed. [H. graminea (Michx. ) Vahl.] 



In still water, Ontario to Oregon, Florida and Mexico. Summer and fall. WATER STAR-GRASS. 



2. Heteranthera liinosa (Sw. ) Willd. Stems 1-5 dm. long, branched, succulent: 

 leaves often numerous ; petioles terete or nearly so, 3-20 cm. long ; blades ovate to oblong- 

 ovate, 1-3 cm. long, obtuse, entire, rounded or subcordate at the base : phyllodes sometimes 

 present : spathe 1-flowered : perianth white or blue ; tube slender, 1.5-2 cm. long; lobes 

 linear, shorter than the tube : seeds delicately ribbed. 



In shallow water or muddy places, Virginia to Missouri, Florida, Louisiana and tropical America. 

 Spring to fall. MUD PLANTAIN. 



3. Heteranthera reniformis R. & P. Stems creeping in the mud, 0.5-4 dm. long, 

 or more elongated : leaves few ; petioles 0.5-2 dm. long ; blades reniform to orbicular- 

 reniform, 3-6 cm. broad, entire, more or less deeply cordate : spathe 2-5-flowered : 



