8 FAMILY KEY 



CC. Leaves entire. 

 D. Leaves i mm. or less wide, 2-10 cm. long; stipules 2 cm. or less long. 



ZannUhettia in Naiadaceae (.p. 34) 

 DD. Leaves 2-4 mm. wide, 0.5-1 cm. long; stipules none. 



Philotria in Hydeocharitaceae (p. 36) 

 BB. Either not water plants, or else tiie leaves alternate or all basal or none or 

 rarely a few of the upper opposite; leaves often more than 5 mm. wide. 

 E. Plants submerged or partly floating, but nothing other than the inflorescence 



rising out of the water. 

 F. Plant stemless; leaves basal, terete, 1-43 mm. in diameter. 



LUaea in Naiadaceae (p. 34) 

 FF. Plants with evident stem; leaves mostly flat, less than 1.5 mm. in diam- 

 eter if terete. 

 G. Leaves either with distinct dilated stipular sheath or with axillary stipules ; 

 .flowers greenish, 4 to many in an umbel-like or spikelike duster. 



Naiadaceae (p. 34) 

 GG. Leaves with neither dilated sheath nor axillary stipules. 

 H. Leaves equitant; flowers 10 or more in a head, monoecious, greenish 

 or whitish. Spakganiaceae (p. 34) 



HH. Leaves not equitant; flowers 1-2 in a cluster, perfect, bright yellow. 



Pontedeeiaceae (,p. si) 

 EE. Plants not submerged nor floating, at least rising out of the water if growing 

 in it. 



I. Flowers in a spadix; leaves resembling those of cat-tails. 



Acorus in Araceae (p. 51) 



II. Flowers not in a spadix; leaves often not as above. 



J. Flowers surrounded by chaffy bracts or bristles or fine hairs, and no other 



perianth present, or no perianth at all. 



K. Cat-tails; perianth of many fine hairs; flowers in a cylindric spikelike 



cluster 10 cm. or more long and 2-2.5 cm. in diameter. Typhaceae (p. 34) 



KK. Not cat-tails; perianth none, or of chaffy bracts, or of stiff usually serrate 



bristles, or of fine hairs {Eriophorum); flowers either not in spikes or the 



spikes smaller. 



L. Perianth of 1-3 chaffy bracts, or of hairs or bristles, or none at all; 

 ovary i-ceUed, i-seeded; stems hollow or not so; flowers often in spike- 

 lets. 

 M. Flowers monoecious, each subtended by 3 chaffy bracts; fruits aggre- 

 gated into spherical burlike heads; growing along borders of ponds in mud 

 or shallow water. Sparganiaceae (p. 34) 



MM. Flowers mostly perfect, each subtended by 1-2 chaffy bracts; 

 fruits rarely aggregated into spherical burlike heads; often growing on 

 dry land. 



N. Leaves 2-ranked; margins of leaf sheath not united; stem hollow in 



nearly all species; fruit a grain. Graminaceae (p. 36) 



NN. Leaves 3-ranked; margins of leaf sheath united; stem solid; fruit 



an akene. Cyperaceae (p. 50) 



LL. Perianth of 6 similar chaffy bracts; ovary either 3-celled or i-celled 



with 3 parietal placentae, 3 to many seeded; stem not hollow; flowers 



not in spikelets. Juncaceae (p. 52) 



