FLORA OF THE DISTRICT OF COLUMBIA. 117 



1. Heteranthera reniformis Ruiz & Pav. Mud plantain. 

 Tide flats and other muddy places or iu shallow water; along the canal, Carberry 



Meadows; Eastern Branch; Hunting Creek. Aug. Eastern U.S. W. Ind., S. Amer. 



2. Heteranthera dubia (Jacq.) MacM. Water star-grass. 

 Quiet shallow water; in the canal, pools along the Potomac, and creek mouths. 



July-Sept. U. S., Cuba, Mex. (Schollera graminea A. Gray.) 



24. JTJNCACEAE. Rush Family. 



Capsule many-seeded, 1-3-celIed; placentae parietal or axial; leaf sheaths open. 



1. JTJNCUS. 

 Capsule 3-seeded, 1-celled: placentae basal; leaf sheaths closed 2. JXJNCOIDES. 



1. JTJNCTJS L. Rush. 



Juncus repens Michx. has been found at Salisbury, Maryland, and may occur within 

 our limits. It would come in the key next to J. marginatum, from which it is distin- 

 guished by its long perianth (6-10 mm. long) and its floating or ascending stems. 



Leaves reduced to bladeless mucronate basal sheaths; leaf of the inflorescence seem- 

 ingly continuous with the stem, the inflorescence therefore appearing lateral. 



Stems tall, erect, naked 1, J. effusus. 



Leaves with well-developed grasslike blades; inflorescence clearly terminal. 

 Leaves hollow, with cross partitions, appearing jointed when dry, usually terete. 

 Seeds with a distinct whitish appendage ("tail") at each end. 

 Seeds loosely covered by the seed coat, the latter prolonged into tails about as 



long as the body of the seed; inflorescence stiff 12. J. canadensis. 



Seeds tightly covered by the seed coat, the latter honeycombed and prolonged 

 into tails only about one-third as long as the seed body; inflorescence loose. 



13. J. subcaudatus. 

 Seeds not tailed, usually with short abrupt dark tips. 



Capsule prismatic, short-pointed 14. J. acuminatus. 



Capsule subulate, with long tapering apex. 



Perianth 4-5 mm. long, the flower heads (exclusive of the beaks of the cap- 

 sules) 12-15 mm. in diameter; 6tamens G; rootstocks slender, 1-2 mm. in 

 diameter, bearing small tubers at intervals of a few centimeters. 



10. J. torreyi. 



Perianth 2.5-3 mm. long, the flower heads (exclusive of the beaks of the cap- 



Bules) 7-10 mm. in diameter; stamens 3; rootstocks stout, uniform, 



2-3 mm. in diameter, even when young 11. J. scirpoides. 



Leaves neither jointed nor with cross partitions, either channeled on the upper sur- 

 face or flattened. 

 Flowers crowded in 2-10-flowered heads, not prophyllate (see below). 

 Heads rath«r few, mostly 5-10-flowered ; stamens shorter than the petals, not 



conspicuotis in fruit 8. J. marginatus. 



Heads very numerous, usually 2-5-flowered ; stamens equaling or surpassing the 



petals, persistent and conspicuous in fruit 9. J. aristulatus. 



Flowers solitary along the branches of the inflorescence, prophyllate (that is, 

 each subtended by two bracteoles in addition to the bractlets at base of 

 pedicel). 

 Plants annual; inflorescence, exclusive of its leaves, more than one-third the 



height of plant 2. J. bufonius. 



Plants perennial; inflorescence, exclusive of its leaves, less than one-third the 

 height of plant. 

 Sepals obtuse, green and dark brown, shorter than or barely equaling the 

 dark brown capsule; stem usually bearing one or two leaves. .3. J. gerardi. 



