8 ELODEACEAE. 



Order HYDROCHARITALES. 



Perennial aquatic herbs with rootstocks. Leaves usually with blades. 

 Flowers monoecious or dioecious, or rarely perfect, from spathes. Perianth 

 double, or corolla wanting. Androecium of 1-12 stamens. Gynoecium 

 3-15-carpellary. Ovary inferior. Fruit capsular or baccate. 



Family 1. ELODEACEAE. Tape-grass Family. 



Plants with leafy stems, or leaves basal, often greatly elongate. 

 Gynoecium 2-5-carpellary, the ovary 1-celled. 



Acaulescent herbs : leaf-blades greatly elongate : staminate flowers with 1-3 stamens. 



1. Vallisneria. 

 Caulescent herbs : leaf-blades relatively short : staminate flowers 



with 9 stamens. 2. riiiLOTRiA. 



1. VALLISNURIA [Mich.] L. Fresh water herbs. Leaves basal, with 

 elongate ribbon-like blades. Flowers dioecious", the staminate numerous, 

 crowded on a spadix, the pistillate few, each solitary at the end of an elongate 

 spiral scape. Fruit sidjtended by the spathe. 



1. V. spiralis L. Leaf -blades narrowly linear, 1-18 dm. long: staminate 

 flowers inconspicuous: pistillate flowers floating: spathe 1-2 cm. long: fruit 

 cylindrie, 3-15 cm. long. ■ — Susquehanna and tributaries. Common, in flowing 

 water. — Sum. — Eel-grass. Tape-grass. 



2. PHILOTRIA Eaf. Fresh water herbs. Leaves cauline, opposite or 

 whorled. Flowers dioecious, polygamous, or perfect, the staminate with 9 

 stamens, the perfect with 3-6 stamens, the pistillate slender-pedicelled. Fruit 

 subtended by the spathe. — Sum. — Water-weed. 



Leaf-blades oblong or ovate-oblong, mostly 1 cm. long or less. 1. P. canadensis. 



Leaf-blades linear, mostly over 1 cm. long. 2. P. angustifolia. 



1. P. canadensis (Michx.) Britton. Leaf -blades 4-15 mm. long, relatively 

 broad, serrulate to the base, sometimes obscurely so: spathes 10-18 mm. long. 

 — N.S. Bather common, in still or slow-flowing water. 



2. P. angustifolia (Muhl.) Britton. Leaves usually less crowded than those of 

 P. canadensis, the upper ones mostly 1-2 cm. long, longer and narrower than 

 the lower ones; blades linear to linear-lanceolate, entire below the middle, 

 remotely toothed above, acuminate. — Susquehanna. Eather rare, in slow- 

 flowing or still water. 



Order POALES. 



Mostly perennial caulescent or acaulescent plants, known as grasses 

 and sedges. Stems sometimes conspicuously jointed. Leaves alternate, 

 mostly sheathing at the base : blades usually narrow and elongate, entire or 

 nearly so. Flowers variously disposed in a simple or compound inflores- 

 cence, perfect or rarely monoecious or dioecious, incomplete, inconspicu- 

 ous, borne in the axils of chaffy bracts or scales (glumes). Fruit a cary- 

 opsis (grain) or an achene, or rarely a nut, or baccate. 



Leaves 2-ranked, their sheaths with un-united margins : stems mostly hollow : fruit 

 a grain (caryopsis). Fam. 1. Poacbae. 



Leaves 3-ranked, their sheaths with united margins : stem 



solid : fruit an achene. Fam. 2. Cyperaceae. 



