144 LEMNACEAE 



Fronds long-stalked mostly submerged, forming large masses l r, trisuica 

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



Frond pale and usually strongly gibbous beneath. 2 L nihba 

 Fronds green or purplish, not gibbous beneath. ^ 



Frond oblong-oboyate. indistinctly 3-nerved. 3 i, minor 

 Frond oblong or elliptical, indistinctly l-nerved or nerveless minor. 



Frond unsymmetrical, without papules. ' 4 L cwlostasa 



Frond symmetrical, with a row of papules along the midvein. I', t minima 



1. L. trisulca L. Fronds usually submerged, seldom floating, usually 

 several generations attached together, oblong to oblong-lanceolate, slightly un- 

 symmetrical and falcate, dentate towards the upper end, 5-10 mm. long, 2-3 mm. 



w M I" TT^•^''^ J,''^''^''?,'^^*^^- N.S.-N.J.— Tex.— Calif.— B.C.; Old 

 World and Austraha. Plain— Mont. Jl-Au. 



2. L. gibba L. Fronds solitary or 2-4 in a group, orbicular to obovate, 2-5 

 mm. long and 2-4 mm. wide, thick, convex and slightly keeled above, with large 

 air-cavities m the gibbous portion, unsymmetrical, 3-5-ncrved. In ponds: Neb. 

 — Tex.-^Ariz.— Cahf.; Mex.; Old World and Australia. Plain—Suhalp . 



3. L. minor L. Fronds solitary or a few together, round to oval, sym- 

 metrical, thickish, convex on both sides, sometimes slightly keeled above and 

 witb a row of papules along the midrib. In stagnant water and slow streams: 

 l.ab.—i? la.— Calif.— Alaska; Mex.; Old World and Australia. Plain— Mont. 



4. L. cyclostasa (EU.) Chev. Frond soUtary or 2-8 in a group, oblong to 

 obovate-oblong, usually somewhat falcate, 2.5-4.5 mm. long, 1-1.5 mm. wide, 

 usually unsymmetrical at the base. L. valdiuiana Philippi. In pools and streams : 

 Mass.— Fla.—Cahf. —Ida.; Mex.— S. Am. Plain— Submont . 



nununa 



s\-mmetrical, 1.5-4 



2-4 



or the lo^^er flat with a thm margin around the frond. In pools : Ga.-Kans. 

 Wyo.— Cahf.; Mex.— S. Am. Plain— Submont. 



2. SPIRODELA Schleiden. Larger Duckweed. 



Frond disk-like several-nerved . Stipe attached peltately to the frond back 

 ?L!f,r "[i^^'\ th^ basal margin. Rootlets several, each with a solitary fibro- 

 vascular bundle. Anthers dehiscent longitudinally, 



•ok ^V. ^' P°^^^**=* (L.) Schleiden. Frond soUtary or in colonies of 2-5, round- 

 ish obovate, flat on both sides, green above, generallv purphsh beneath, 5-15- 



!^f'"!f ' M'^'i T^""- ^'"'^^^ ^^^^ ^-k-^ "^'"- ^«"g; '•ootlets 4-16. In pools and 

 ponds: N.S.— B.C.— Fla.— Mex.; Old World and S. Am. Plain. 



Family 16. COMMELINACEAE. Spiderwort Family. 



Somewhat succulent herbs, with fibrous or tuberous-thickened roots and 

 alternate leaves sheathing at the base. Flowers perfect, subtended by leaf- 

 like sheathing bracts. Sepals 3, herbaceous. Corolla regular or irregular, 

 with 3, usua ly showy, colored petals. Stamens 6 or 5, sometimes 2 or 3 

 of these sterile. Gynoecmm of 2 or 3 united carpels; ovary superior, 2- or 

 3-celled; styles united. Fruit a loculicidal capsule. 



Petals aU alike: perfect stamens 6; bracts leaf-like. 1 TRAnFsrAxriA 



Petals unlike m shape and size; perfect stamens 3 or 2; bracts spathe-Uke 



2. COMMELINA. 



1. TRADESCANTIA (Rupp.) L. Spiderwort. 



Caulescent perennials, with alternate narrow leaves. Cymes umbel-like, 

 !n^}^^-' f-^^i^^^^ by usually 2 bracts, similar to the leaves. Sepals 3, nearly 

 equa , distinct. Petals 3, sho^T, blue, rose-color or white, .sessile .similar and 



equal, „j 



Capsule locuhcidal, 3-vaived. Seeds 3-^ 



hairy 



.ais giaiiumar-piiose; petals about 15 min. long; capsule decidedly elliDsoid 



u^ufJmu?^^^^ ^^°"^i^ gibbous^t ^the'^K "^.tem ^^^^^ dm. high, 



usually simple; pod densely glandular. 1 r hracteata. 



