2(1). Lip with prominent curved basal lateral teeth; lamina less than 6 mm. long; 



stem green 2. L. cordata. 



2. Lip slightly auriculate at the base but without lateral teeth; lamina more than 



6 mm. long; stem purplish 3. L. aiistralis. 



1. Listera convallarioides (Sw.) Nutt. Broad-leaved twayblade, broad-lipped 



TWAYBLADE. Fig. 364. 



Plants slender or occasionally stout, stoloniferous, glabrous below, densely 

 and minutely whitish glandular-pubescent above, 6-37 cm. tall; leaves two, 

 opposite or occasionally subopposite, mostly above the middle of the stem, broadly 

 ovate to elliptic, oval or suborbicular, obtuse or rarely acute to apiculate, glabrous, 

 2-7 cm. long, 1.5-5.8 cm. wide; raceme loose, laxly many-flowered, 2-12 cm. 

 long, 2.5-4 cm. in diameter; floral bracts rhombic-ovate, acute to acuminate, 

 semitranslucent, 3-5 mm. long; flowers yellowish green, with slender pedicels 

 which are 4-7 mm. long; dorsal sepal ovate-lanceolate, narrowly obtuse to acute, 

 4.5-5 mm. long, about 1.8-2 mm. wide; lateral sepals lanceolate, strongly falcate- 

 recurved, acute to subacute, 1 -nerved, 4.5-5.5 mm. long, 1.5-1.8 mm. wide below 

 the middle; petals linear-falcate, obtuse, 1 -nerved, 4-5 mm. long, 0.8-1 mm. 

 wide; lip with a short slender claw, narrowly cuneate, shallowly notched at the 

 apex, with the lateral lobules obtusely rounded, minutely toothed in the sinus, 

 with a short triangular tooth on each side near the base, minutely bristly-ciliate 

 along the margins, 8-13 mm. long, 5-7 mm. wide near the apex; column slender, 

 slightly recurved, 2.5-3 mm. long; capsule nearly glabrous. 



In leaf mold in damp mossy coniferous or mixed coniferous-hardwood forests, 

 bogs, meadows, various types of evergreen swamps, wet thickets in forests and in 

 peaty barrens, in Ariz. (Pima Co.), June-Sept.; Nfld. and Ont. to Alas., s. to 

 Ariz. 



2. Listera cordata (L.) R. Br. Heart-leaved twayblade. Fig. 364. 



Plant slender, delicate, glabrous throughout (except for a small glandular- 

 pubescent area just above the leaves), 6.5-25 cm. tall; roots often somewhat 

 matted; leaves 2, opposite, about midway up the stem, broadly to narrowly ovate- 

 cordate or deltoid, mucronate, 0.9-4 cm. long, 0.7-3.8 cm. wide; raceme densely 

 or loosely flowered, slender, 2-10 cm. long, 8-15 mm. in diameter; floral bracts 

 small, purplish to yellowish-green, with slender pedicels which are 1-4 mm. long; 

 dorsal sepal ovate-oblong to oblong-elliptic, obtuse, 2-3 mm. long, about 1 mm. 

 wide; lateral sepals ovate-oblong to elliptic or oblong-linear, obtuse, somewhat 

 oblique, 2-3 mm. long, 0.5-1.5 mm. wide; petals elliptic to oblong-linear, obtuse 

 or occasionally truncate, 1.5-2.5 mm. long, 0.5-1 mm. wide; lip linear-oblong, 

 cleft one-half to two thirds of the distance to the base into two linear-lanceolate 

 lobes, with a subulate transverse tooth on each side near the base, the lamina 

 being 3-6 mm. long and 1-1.5 mm. wide near the middle; column short, about 

 0.5 mm. long. 



In mossy damp coniferous or mixed coniferous-hardwood forests, sphagnum 

 bogs, various kinds of evergreen swamps and in subalpine forests and thickets, 

 in N. M. (Pecos River National Forest), Apr.-Sept.; Greenl. and Nfld. to Alas., 

 s. to N.C., Wyo., N.M. and Calif.; Icel., Eur. and Jap. 



3. Listera australis Lindl. Southern twayblade. Fig. 365. 



Small inconspicuous terrestrial herb with fibrous matted roots; stem slender, 

 rarely more than 15 cm. high, more or less glandular-pubescent above the two 

 opposite or subopposite leaves; leaves sessile, inserted above the middle of the 

 stem, typically ovate-elliptic, to 4 cm. long; inflorescence a terminal raceme com- 

 posed of small reddish-purple or greenish flowers; sepals and petals free, similar 



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