ALISMACE^E. 225 



4. Sagltta'rla. Flowers monoecious, sometimes dioecious. Stamens 

 numerous. Carpels numerous, in more or less globular heads. 

 Leaves arrow-shaped, but varying greatly. Flowers mostly in 

 whorls of 3 on the scapes, the sterile ones uppermost. 



1. TBIGLO'CHIM, L. ARROW-GRASS. 



1. T. palUS'tre, L. A slender rush-like plant, 6-18 inches 

 high, found growing in bogs northward. Carpels 3, awl- 

 pointed at the base, splitting away from below upwards. 

 Spike or raceme slender, 3 or 4 inches long. 



2. T. marit'imum, L. The whole plant is stouter than 

 No. 1, and the carpels are usually 6 in number. Atl. sea- 

 coast, and saline marshes. 



2. SCIIKI CIIZE RIA, L. SCHEUCHZERIA. 



S. palustris, L. Stem zigzag. Flowers in a loose terminal 

 raceme, with sheathing bracts. Bogs. 



3. AMS .MA, L. WATER-PLANTAIN. 



A. Planta'gO, L., var. America' num, Gray. Leaves 

 long-petioled, mostly oblong-heart-shaped, but often nar- 

 rower, 3-9-nerved or ribbed, and with cross veinlets between 

 the ribs. Flowers small, white, in a large and loose com- 

 pound panicle. Low and marshy places, often growing in 



the water. 



4. SAGITTA'RIA, L. ARROW-HEAD. 



* Filaments narrow, as long as the anthers. 



1. S. varia'bilis, Engelm. Very variable in size and in 

 the shape of the leaves. Scape angled. Common every- 

 where in shallow water. 



Var. obtusa, Engelm., is dioacious, and has large obtuse 

 leaves. 



Var. latifolia, Engelm., is monoecious, with large broad 

 acute leaves. 



Var. angUStifo'lia, Engelm., has narrow leaves, with 

 long and linear diverging lobes. 



* * Filaments very short, with enlarged mostly glandular base. 



2. S. heterophyl'la, Pursh. Scape weak and at length 

 procumbent. Leaves lanceolate or lance-ovate, entire, or 

 with one or two narrow basal sagittate appendages. 



