46 MISC. PUBLICATION 4 2 3, U. S. DEPT. OF AGRICULTURE 



3. Stems very short or none, the plants floating; inflorescences subtended by 

 spathes (4). 

 4. Plants reduced to small frondlike floating bodies without differentiation 

 of stem and leaf; inflorescence 2- or 3-flowered, borne on the edge 



of the frond 12. Lemnaceae. 



4. Plants differentiated but stem very short; leaves in a rosette, with 

 broadly obovate blades and short petioles; inflorescence several 



flowered; spathe white 11. Araceae. 



1. Plants terrestrial or semiaquatic or, if strictly aquatic, then the perianth 



relatively large and showy (5). 



5. Perianth none or very rudimentary, reduced to bristles or minute scales (6). 



6. Flowers not individually subtended by scales or assembled in spikelets, 



unisexual, very numerous in a dense cylindric spike with the staminate 



flowers above 3. Typhaceae. 



6. Flowers individually subtended by scales (glumes) and assembled in 



spikelets, these sometimes reduced to 1 flower; leaves with a sheathlike 



basal portion enclosing the stem (7). 



7. Stems round or flat, usually hollow except at the joints; leaves 2-ranked, 



the sheath commonly split; flowers with a 2-nerved scale (palea) 



next to the axis 8. Gramineae. 



7. Stems often triangular, usually solid; leaves 3-ranked, the sheath not 

 split; flowers without a 2-nerved scale next to the axis. 



9. Cyperaceae. 

 5. Perianth evident, at least in the pistillate flowers (8). 



8. Divisions of the perianth not showy, greenish or brownish; plants mostly 

 of wet ground (9) . 

 9. Perianth relatively large, regular, the 6 divisions resembling the glumes 



of grasses in texture; flowers perfect 16. Juncaceae. 



9. Perianth small (10). 



10. Flowers unisexual, in dense round heads, the fruiting inflorescences 

 burlike; perianth of the pistillate flowers irregular, the divisions 

 chaffy, the staminate flowers naked 4. Sparganiaceae. 



10. Flowers perfect, in slender elongate racemes; perianth regular, the 



divisions not chaffy or glumelike 6. Juncaginaceae. 



8. Divisions of the perianth (at least the inner ones) showy, petallike (11). 



11. Plants trees, with a tall trunk; leaf blades fan-shaped, many ribbed, 



deeply lobed 10. Palmae. 



11. Plants not trees or, if treelike, then the leaves not fan-shaped 



or lobed (12). 



12. Plants epiphytic (growing on the branches of trees). 



13. Bromeliaceae. 

 12. Plants terrestrial (rooted in soil), or aquatic (13). 



13. Pistils several or many, in a head or ring; ovary 1-celled; flowers 



perfect or unisexual 7. Alismaceae. 



13. Pistil one; ovary usually 3-celled, or the ovules on 3 placentae; 

 flowers mostly perfect (14). 

 14. Stamens more than 3, commonly 6, some of them (in genus 

 Commelina) often imperfect (15). 

 15. Perianth adnate below to the ovary and appearing as if 



borne upon it 18. Amaryllidaceae. 



15. Perianth free from the ovary or nearly so (16). 



16. Segments of the perianth sharply differentiated, the outer 

 ones green, sepallike, the inner ones petallike, fugacious, 

 not bearing glands; flowering stems not from a 



bulb 14. Commelinaceae. 



16. Segments of the perianth not sharply differentiated or, if 

 so (in genus Calochortus) , then the inner ones bearing 

 a conspicuous fringed gland and the flowering stems 



from a bulb 17. Liliaceae. 



14. Stamens 3 or fewer (17). 



17. Perianth very irregular, adnate below to the ovary; stamens 

 1 or 2; flowers not subtended by spathes. 



20. Orchidaceae. 

 17. Perianth regular or very nearly so; stamens 3; flowers sub- 

 tended by spathelike bracts (18). 



