36 HYDROCHARITACEAE (WATER-WEED FAMILY) 



or pink, of 5 deciduous imbricate petals. Stamens 6 or more. 

 Fruit a head or whorl of separate flat or turgid akenes. — Diffictdt 

 family. Key only to genera. (F. & R. p. 35.) 



A. Leaves not sagittate, although sometimes cordate at base; flowers in compound 

 panicles, perfect; akenes in a whorl ; receptacle depressed. — {Celtic alls = water; 

 from the habitat.) Alisma (water plantain) 



AA. Leaves sagittate; flowers in whorls or 3 near the top of the scape, monoecious 

 or dioecious; akenes in a head; receptacle convex to globose. — (L. sagilla = an 

 arrow; referring to leaf form.) Sagittaria (wapato) 



HYDROCHARITACEAE (Water-weed Family) 



Perennial; submerged, with stem elongated. Leaves whorled, 

 sessile, pellucid, i-veined, oblong or ovate-oblong, usually obtuse, 

 5-10 mm. long, 2-4 mm. wide, margin usually minutely dentic- 

 ulate or serrulate. Flowers very rare. W. E. — Only the follow- 

 ing species. (Gk. phyllon = a leaf, freis = 3 ; the leaves are often 



in 3's.) Philotria canadensis (WATER weed) 



GRAMINACEAE (Grass Family) 



Herbs, annual or perennial; stems terete, usually hollow, their 

 joints closed. Leaves sheathing, with scarious ring (ligule) 

 where blade joins sheath; sheath usually split to base on side oppo- 

 site the blade. Inflorescence various, but its elements composed 

 of flower groups (spikelets) of i to many flowers. Spikelets com- 

 posed of 0-2 basal flowerless bracts (glumes), above which are other 

 bracts usually in pairs (the outer = lemma, the inner = palet) 

 and each pair inclosing a flower or an abortive one. Lemma and 

 glume often awned. Palet with back to axis (rachilla) of spikelet, 

 opposite its lemma and often rolled up in it. Stamens 1-6, usually 

 3; anthers versatile. Styles 1-3, usually 2 and lateral; stigmas 

 plumose or hairy. Fruit i-seeded, a grain. — A difficult family. 

 The key is to species usually only when of economic importance. 

 (F. & R. pp. 36-74.) 



A. Grain in com-ear-like cluster. MAYDEAE (p. 37) 



AA. Grain not in corn-ear-like cluster. 



B. Spikelets i -flowered, rarely 2 -flowered, terete or dorsally flattish (laterally in 

 Oryseae) ; imperfect flower below'in the 2-flowered spikelets. 

 C. Glumes 1-2 ; spikelets terete or dorsally flattened, 1-2-flowered. 

 D. Glumes indurated; lemma and palet of fertile flower hyaline; stamen i. 



ANDROPOGONEAE (p. 37) 



DD. Glumes membranous; lemma and palet of fertile flower indurated; 



stamens 3. PANICEAE (p. 38) 



