48 POACEAE 



2. Philotria angustifolia (Muhl.) Brittou. Stems slender, mostly 3-10 dm. 

 long: leaf -blades linear, 1-2 cm. long, acute, minutely serrulate: spathe of the 

 staminate flowers ovoid, 2-3 mm. long: sepals and petals of the staminate flowers 

 elliptic or oval, 2 mm. long or less: pistillate flowers with a hypanthium 3-10 cm. 

 long and elliptic sepals and petals 1.5-2 mm. long. 



In slow streams, New York to Florida. 



3. Philotria minor (Engelm.) Small. Stems very slender, mostly 3-5 dm. long: 

 leaf-blades linear, 5-8 mm. long, acutish, decidedly serrulate: spathe of the staminate 

 flowers ovoid, about 4 mm. long: sepals and petals of the staminate flowers oval, 

 1-1.5 mm. long: pistillate flowers with a hypanthium 2-5 cm. long and elliptic sepals 

 and petals 1-1.5 mm. long. 



In slow streams, ponds and lakes, Wisconsin to Kentucky, Kansas and Arkansas. 



4. Philotria linearis Eydb. Stems slender, mostly 2-5 dm. long : leaf -blades 

 linear, about 1 cm. long, acute, very obscurely serrulate : spathe of the staminate 

 flowers ovoid, about 3 mm. long: sepals of the staminate flowers broadly oval, 2.5 mm. 

 long; petals oblong, shorter than the sepals: pistillate flowers not seen. 



In swamps along the Cumberland River, near Nashville, Tennessee. 



Family 2. HYDROCHARITACEAE Aschers. Frog's-bit Family. 



Plants with leaves in clusters on the rootstocks. Gynoecium 6-9-earpellary, 

 the ovai-y 6-9-celled. 



Flowers dioecious: stamens distinct: anthers nearly sessile: leaves not difTerentiated into blade and 

 petiole. 1. Thalassia. 



Flowers monoecious: stamens with united filaments: leaves differentiated into blade 



and petiole. 2. Limnobium. 



1. THALASSIA Banks. 



Marine herbs. Leaves mere strap-like blades. Flowers dioecious. Fruit rugose 

 or nearly echinate. Turtle Grass. 



1. Thalassia testudinum Koenig & Sims. Leaves 2-5 together ; blades linear, 

 5-30 cm. long: fruit echinate-pubescent, erect. 



In shallow water, coast of peninsular Florida. Also in the West Indies. 



2. LIMNOBIUM L. C Eich. 



Fresh-water herbs. Leaves with dilated blades terminating petioles. Flowers 

 monoecious. Fruit smooth. Frog's-bit. 



1. Limnobium Spdngia (Bosc) L. C. Eich. Leaves several together; blades 

 ovate to suborbicular or reniform, 2-5 cm. broad: fruit glabrous, nodding. 

 In shallow water or mud, Ontario to Illinois, Missouri, Florida and Louisiana. 



Order 5. POALES. 



Mostly perennial caulescent or acaulescent plants, commonly known as 

 GRASSES and SEDGES. Stems (culms) simple or branched, sometimes conspicu- 

 ously jointed. Leaves alternate, mostly sheathing at the base: blades usually 

 narrow and elongated, entire or nearly so. Flowers variously disposed in a 

 simple or compound inflorescence, perfect, or rarely monoecious or dioecious, 

 incomplete, inconspicuous, borne in the axils of chaffy bracts or scales (gliunes). 

 Fruit a caryopsis (grain) or an achene. 



Leaves 2-ranked, their sheaths with ununited margins: stems mostly hollow: fruit a grain (caryopsis). 



Fam. 1. PoACEAE. 

 Leaves 3-ranked, their sheaths with united margins: stems solid: fruit an 



achene. Fam. 2. Cvperaceae. 



Family 1. POACEAE R.Br.' Grass Family. 



Annual or perennial herbs, or rarely shrubs or trees, sometimes monoe- 

 cious or dioecious, varying much in habit. Stems (culms) usually hollow, the 

 nodes closed. Leaves alternate, 2-ranked, sheathing, the sheaths generally open 

 to the base on the side opposite the blade; a scarious or cartilaginous ring 



^ Contributed by Mr. George V. Nash. 



