a distinct midvein, to 15 cm. long; sheaths thin, tipped on either side with small 

 acute stipulelike appendages; spathe terminal, 1 -flowered, rarely more than 2 

 cm. long, exposed above the water; perianth pale yellow, with an elongated 

 filiform tube rarely more than 3 cm. long and a rotate 6-parted limb, the seg- 

 ments linear-lanceolate and to about 1 cm. long; stamens 3, equal in size, the 

 filaments dilated below; stigma several-lobed; capsule 1 -celled, with 3 parietal 

 placentae; seeds oblong-ovoid, finely crosslined, with prominent raised mem- 

 branous longitudinal ribs. Zosterella dubia (Jacq.) Small. 



Streams, canals and quiet waters in e. Okla. (Mayes Co.), s. and s.-cen. Tex. 

 and Ariz. (Maricopa and Yavapai cos.), Apr.-June; Fla. to Tex., Ariz., Calif, 

 and Mex., n. to Que. and Ont., w. to Ore. 



2. Heteranthera Liebmannii (Buch.) Shinners. Fig. 308. 



Plant similar in habit and habitat to H. dubia; spathe to 6 cm. long; perianth 

 tube to 12 cm. long. Zosterella longituba Alex. 



On mud or floating in ponds and ditches in s. and w. Tex., Apr.-July; Tex. 

 and Ala., s. to Mex. and W.I. 



This species is more abundant in Texas than the closely allied H. dubia. 



3. Heteranthera liniosa (Sw.) Willd. Fig. 308. 



Plants rooted in mud to form rosettes, also represented by another distinct 

 form with an elongated creeping stem that roots at the nodes; leaf blade ovate 

 to elliptic or elliptic-lanceolate, to 1 dm. long, usually much shorter; spathe 

 conspicuously peduncled, 1 -flowered; flowers white to purplish-blue. 



Ponds, tanks and in wet soil of low woods in Okla. (Alfalfa, Cherokee, 

 Comanche and Johnston cos.), s., cen. and w. Tex., rare in e. Tex., w. to N. M. 

 (Grant and Socorro cos.) and Ariz. (Graham. Cochise and Santa Clara cos.), 

 May-Oct.; Fla., w. to Ariz, and Mex., n. to Minn., Neb. Colo.; also trop. Am. 



What we consider to be two forms of this species, as noted above, might 

 prove to be distinct entities with further study. 



4. Heteranthera reniformis R. & P. Fig. 309. 



Plants creeping in mud or floating in shallow water; leaf blades round-reniform, 

 to 3 cm. long and 5 cm. wide; spathe short-peduncled, 3- to 10-flowered; flowers 

 white or pale-blue. H. peduncularis Benth. 



In streams in w. and s.e. Tex., Aug. -Sept.; Fla., w. to Tex. and Mex., n. to 

 Conn., 111. and Neb. 



4. Eurystemon Alex. 

 A monotypic genus. 

 1. Eurystemon mexicanum (Wats.) Alex. Fig. 309. 



Erect herb rooted in mud, to 4 dm. tall, noticeably glandular-pubescent above; 

 leaves sessile, sheathing the stem, to 15 cm. long, straplike; flowers about 12 

 in open spike that appears to be terminal, pale-blue to indigo-blue, from a spread- 

 ing foliaceous spathe; perianth salverform, the limb conspicuously zygomorphic; 

 stamens 3, strikingly dissimilar; anthers basifixcd, anther on longest filament bluish 

 and much larger than those on the two short inflated filaments; capsule 3-celled, 

 many-seeded. Heteranthera mcxicana Wats. 



In ditches and about ponds in s. and n.w. Tex., June-Aug.; also n. Mex. 



Fam. 34. Juncaceae Juss. Rush Family 



Annual or perennial grasslike or sedgclike herbs, usually growing in wet places; 

 leaves (like those of Cyperaceae and Gramineae) definitely formed into a lower 

 sheath and an upper blade or the latter reduced in some species; inflorescence a ter- 



604 



