4 ZANNICHELLIACEAE. 



Pollen-grains simple : pistillate part of the rachis with persistent pedicels 1 mm. long 

 or less. 1. T. angustifolia. 



Pollen-grains in 4"s : pistillate part of the rachis with persistent 



pedicels 2-3 mm. long. 2. T. latifolia. 



1. T. angustifolia L. Stem slender, 1.5-3 m. tall: leaf -blades 5-15 mm. wide: 

 spike brown, the pistillate portion 0.5-1.5 cm. thick, separated from the 

 staminate: stigmas narrow: nutlets terete. — Eare, in shallow water or mud. 



2. T. latifolia L. Stem stout, 1-2.5 m. tall: leaf -blades 10-25 mm. wide: spike 

 dark-brown or black, the pistillate portion 2..5-3 cm. thick, contiguous to the 

 staminate : stigmas spatulate or rhomboidal : nutlets furrowed. — Common, in 

 ponds and still water. 



Family 2. SPARGANIACEAE. Bur-reed Family. 



Spikes in racemes or panicles, or spicate, their bracts persistent. 

 Perianth of scales. Pistil sessile : stigma subulate, sometimes oblique. 



1. SPARGANIUM [Tourn.] L. Plants growing in low grounds or deep 



water. Leaves erect and triangular-keeled at the base or floating and flat. — 



Sum. — Bur-reed. 



Achenes fusiform, the body stalked. 



Inflorescence branched, the branches geniculate and bearing 3 or more staminate 

 spikes. 1. S. androcladum. 



Inflorescence simple, or if branched the branches strict and 



bearing less than 3 staminate spikes. 2. S. atnericanum. 



Achenes obovoid or obpyramidal, sessile. 3. S. eurycarpum. 



1. S. androcladum (Engelm.) Morong. Plants 2-7 dm. tall, branched: stami- 

 nate heads mostly less than 1 cm. thick: fruit-heads 1-2 cm. thick: achene-body 

 6-7 mm. long, abruptly narrowed at the apex, long-stipitate. — N.S. Common, 

 in shallow water. — Sandstones and shales, schists. 



2. S. americanum Nutt. Plants 2-8' dm. tall, simple, the lower flower-heads 

 sometimes peduncled: achene-body about 5 mm. long, short-stipitate, gradually 

 narrowed at the apex. — M. Bare, in shallow water. — Limestones. 



3. S. eurycarpum Engelm. Plants 8-20 dm. tall: staminate heads about 1 cm. 

 thick: fruit-heads 2.5-3 cm. thick: achene-body 7-8 mm. long, rounded or 

 depressed at the apex, sessile. — Susquehanna valley. Eather rare, in shallow 

 water. 



Order NAIADALES. 



Perennial, aquatic or marsh herbs. Leaves various, sometimes mere 



phyllodia. FloAvers usually symmetrical. Perianth wanting or imperfect. 



Androecium usually of 1^ stamens. Gynoecium simple or several- 

 carpellary. 



Gynoecium of distinct carpels : anthers with petal-like connectives : leaf -blades not 



spiny-toothed. Fam. 1. Zankichelliaceae. 



Gynoecium of united carpels : anthers with inconspic- 

 uous connectives : leaf-blades spiny-toothed. Fam. 2. Naiadaceae. 



Family 1. ZANNICHELLIACEAE. Pondweed Family. 



Aquatic caulescent herbs. Leaves alternate, filiform,__or with blades, 

 entire. Flowers perfect or monoecious, in spikes or clusters from a spathe. 

 Androecium of 1, or mostly 2-A, distinct stamens. Gynoecium of several 

 distinct carpels. Fruit a cluster or spike of drupelets. 



1. POTAMOGETON [Tourn.] L. Herbs growing mostly in fresh water. 

 Leaves various, the submerged and the floating ones usually different. Flowers 



