ANALYTICAL KEY 11 



M. Perianth free from the ovary or none N. 



N. Perianth wanting or of scale-like or bristle-form divisions O, 



O. Flowers inclosed or subtended by imbricated husk-like 



scales (glumes) ; grass-like plants with jointed stems, 



sheathing (mostly narrow) leaves, and 1-seeded fruit. 



Stems hollow, round or flattened; leaf-sheaths split; 



anthers attached by the middle Gramineae, 86 



Stems usually more or less triangular, solid ; leaf-sheaths 



not split ; anthers attached at the base Cyperaceae, 171 



O. Flowers not inclosed in husk-like scales (though sometimes in 

 involucrate heads) P. 

 P. Immersed aquatics, branching and leafy, the upper leaves 

 often floating. 

 Flowers perfect Najadaceae, 69 



Flowers monoecious or dioecious. 

 Flowers in globose heads Sparganiaceae, 68 



Flowers axillary, solitary Najadaceae, 69 



P. Terrestrial or marsh plants Q. 

 Leaves petioled, the blade net-veined Araceae, 257 



Q. Leaves linear or sword-shaped, parallel-veined, not petioled R. 

 R. Flowers monoecious or dioecious. 



Flowers in cylindrical spikes Typhaceae, 67 



Flowers in heads. 

 Heads spheroidal, pubescent, involucrate Eriocaulaceae, 260 

 Heads globose, glabrous, not involucrate Sparganiaceae, 68 

 R. Flowers perfect. 



Flowers in a dense spike, this borne on the margin 



of a 2-edged scape ; root aromatic Acorus, 258 



Scapes or peduncles cylindrical. 



Ovaries 3-6, separating at least when ripe Juncaginaceae, 79 

 Ovary single, 3-carpeled Juncaceae, 267 



N. Perianth always present, herbaceous or colored, neither scale- 

 like nor bristle-form S. 

 S. Pistils numerous in a head or ring Alismaceae, 80 



S. Pistil one, compound (cells or placentae mostly 3) T. 

 T. Stamens 3. 



Moss-like, aquatic ; flowers solitary IVIayacaceaEj 263 



Rush-like marsh or bog plants ; flowers in spikes, racemes, 

 or heads. 

 Flowers racemose or spicate Juncagixaceae, 79 



Flowers in dense scaly heads Xyridaceae, 262 



T. Stamens 4 Maianthejnum, 291 



T. Stamens 6 U. 

 U. Stamens all alike and fertile. 



Gray scurfy moss-like epiphyte Bromeliaceae, 265 



' Not epiphytic. 



Ovary of nearly separate carpels Juncaginaceae, 79 



Ovary (often angled or lobed) not deeply cleft. 

 • Divisions of the perianth alike or nearly so. 



Perianth woolly Haemodoraceae, 296 



Perianth not woolly. 

 Plant rush-like; perianth small, greenish or 



purplish brown Juncacsae, 267 



