348 



WEEDS AND USEFUL PLANTS. 



staminate ones above. Calyx green and persistent. Petals white, decid* 

 uous, imbricated in the bud. Stamens numerous; anthers extrorse. 

 Ovaries many, in depressed-globose heads, in fruit becoming flattened 

 winged akenes. Smoothish perennials ; roots often tuberiferous ; leaves 

 polymorphous, usually sagittate ; scape sheathed at the base by the bases 

 of the long cellular petioles. 



i, S. varia'bilis, Engelmann. Scape simple or branc A ; leaves 

 very various, mostly sagittate ; pedicels of the fertile florvi about half 

 the length of the sterile ones ; filaments awl-shaped, it^'Aj twice the 



Fig, 243. Tlis Arrowhead (Sagittaria variabilis 



