Sagittaria 



Alismaceae 



89 



Sagittaria cuneata Sheldon 



Terminal lobes of leaves of an ovate type, wider than linear. 



Apex of terminal lobe of leaves acute; plants usually monoecious; scapes 



usually terete 1. S. latifolia. 



Apex of terminal lobe of leaves obtuse or rounded; plants usually dioecious. 



la. S. latifolia var. obtusa. 



Terminal lobes of leaves linear lb. S. latifolia f . gracilis. 



Bracts lanceolate or long-cuneate, usually long-acuminate at the apex, sometimes 



merely acute in Sagittaria cuneata; beaks of achenes erect or if curved, bent 



outward from an erect base. 



Beaks of achenes very short, less than 0.5 nun long, usually about 0.3 mm long; 



achenes 2-2.5 (3) mm long, strongly obovoid, their faces not keeled or 



crested; leaves mostly 4-15 cm long, sagittate or sagittate-hastate; bracts 



mostly 6-12 mm long 2. S. cuneata. 



Beaks of achenes 0.5-2 mm long, usually about 1.5 mm long, arising from the 



inner edge of the achene and forming with the top of the achene a minute 



sinus, sometimes some of the beaks diverging; achenes keeled on each face 



and their margins more or less notched. 



Each face of the achene with a single keel ; sinus at the top of achene (between 



the wing and beak) wide and rounded; scapes strongly ribbed; bracts 



acuminate, mostly 8-25 mm long 3. S. brevirostra. 



Each face of the achene with two or more crested keels and sometimes with one 

 or two short, intermediate ones ; sinus at the top of the achene deeper and 



narrower, sometimes almost closed by the outwardly curved beak 



4. S. australis. 



Leaves all entire or with a few leaves lobed; blades linear, lanceolate, or elliptic; 

 filaments of stamens more or less glandular-pubescent; plants growing in shallow 

 water or in very wet places. 

 Pistillate heads sessile; beak of achene about 1.5 mm long; body of achene about 



3 mm long 5. S. rigida. 



Pistillate heads pedicellate; beak of achene very short, mostly 0.3-0.75 mm long, 

 lateral; body of achene about 2 mm long 6. S. graminea. 



1. Sagittaria latifolia Willd. Common Arrowhead. Map 109. The ex- 

 treme variability of the leaves of this species has led authors to describe 

 several forms, one of which has been reported from Indiana. I think that 

 much of the variations in leaf pattern is due to habitat. This species is 



