SEDGE FAMILY 49 



Perigynia ovoid; fertile culms rarely if ever fllamentose at the base; plant loosely 

 stoloniferous. 156. C. saxatilis. 



Perigynia from little to much inflated; beak bidentate; stigmas normally three and 

 achenes triangular. 

 Pistillate spikes globose or short-oblong, 5-15-flowered. 157. C. oligosperma. 



Pistillate spikes oblong to cylindric, 15-many-flowered. 



Lower perigynia not refle.xed; bracts moderately exceeding the spikes. 



Perigynia ascending; lower sheaths more or less strongly fllamentose; culms 

 sharply triangular. 

 Perigynia" 6-8 mm. long. 



Perigynia oblong-ovoid, tapering into the beak; spikes loosely flowered 



at base. 158. C. Raeana. 



Perigynia ovoid or globose-ovoid, contracted into the beak; spikes more 

 closely flowered. 159. C. vesicaria. 



Perigynia 8-10 mm. long, tapering into the beak. 160. C. exsiccala. 

 Perigynia spreading at maturity; lower sheaths not fllamentose; culms bluntly 

 triangular below the spikes. 161. C. rostrata. 



Lower perigynia reflexed; bracts many times exceeding the spikes. 



162. C. retrorsa. 



Family U. ARACEAE. Arum Family. 



Spadix terminal, with an oblong shea tiling spathe; leaves petioled, with broad blades. 



1. Lysichiton. 

 Spadix borne somewhat laterally on the leaf-like scape; spathe leaf-like, continuous to 

 the scape; leaves narrowly linear, equitant. 2. AcoRUS. 



1. LYSICHITON Schott. Skunk Cabbage. i. L. kamtschatcensis. 



2. ACORUS L. Sweet Flag, Calamus-root. l. A. Calamus. 



Family 15. LEMNACEAE. Duckweed Family. 



Rootlets solitary, without a flbro-vascular bundle. 1. Lemn.\. 



Rootlets several, each with a flbro-vascular bundle. 2. Spirodela. 



1, LEMNA L. Duckweed. 



Fronds long-stalked, mostly submerged, forming large masses 1. L. trisulca. 



Fronds short-stalked or sessile, floating on the surface. 



Frond pale and usually strongly gibbous beneath. 2. L. gibba. 



Fronds green or purplish, not gibbous beneath. 



Frond oblong-obovate. indistinctly 3-nerved. 3. L. minor. 



Frond oblong or elliptical, indistinctly 1-nerved or nerveless. 



Frond unsymmetrical, without papules. 4. L. cyclnstasa. 



Frond synimetrical, with a row of papules along the midvein. 5. L. minima. 



2. SPIRODELA Schleiden. Larger Duckweed. l. S. polyrhiza. 



Family 16. COMMELINACEAE. Spiderwort Family. 



Petals all alike; perfect stamens 6; bracts leaf-like. 1. Tradescantia. 



Petals unlike in shape and size ; perfect stamens 3 or 2 ; bracts spathe-like. 2. Commelin.\. 



1. TRADESCANTIA (Rupp.) L. Spiderwort. 



Sepals glandular-pilose; petals about 15 mm. long; capsule decidedly ellipsoid. 



Bracts broader than the leaves, strongly gibbous at the base; stem 2-3 dm. high, 



usually simple; pod densely glandular. 1. T. bracteata. 



Bracts not broader than the leaves, not strongly gibbous at the base; stem usually 

 over 3 dm. high, branched. 

 Pod densely glandular-pubescent; sepals broadly lanceolate, densely glandular; 

 plant bright green; branches shorter than the stem proper. 2. T. occidentalis. 

 Pod glabrate. pubescent only in lines or at the apex. 



Pedicels strongly glandular; pods pubescent in lines; branches almost equalling 



the stem. 3. T. larimiensis. 



Pedicels glabrous or slightly glandular above; pods pubescent only at the apex. 



4. T. universitatis. 

 Sepals glabrous or nearly so; petals about 10 mm. long; capsule subglobose. 



3. T. scopulorum. 



2. COMMELINA (Plum.) L. Day-flower, Dew-flower, i. C. crispa. 



Family 17. PONTEDERIACEAE. Pickerel-w^eed Family. 



stamens unequal, the 2 posterior ones with ovate anthers, the third with a sagittate 

 anther; capsule incompletely 3-ceIled; leaf-blades broad, long-petioled. 



1. Heter.\nthera. 



Stamens all alike; anthers all sagittate; capsule 1-celled, with 3 parietal placentae; leaf- 

 blades linear, translucent, sessile. 2. Zosterell.v. 



1. HETERANTHERA R. & P. Mud-plantain. l. H. limosa. 



2, ZOSTERELLA Small. Water Star-grass. i. Z. dubia. 



