NAIADACE^E. (PONDWEED FAMILY.) 361 



Order 85. ALISM ACE Hi. (Water-Plantain Family.) 



Marsh herbs, with seape-like stems, sheathing leaves, and perfect or 

 monoecious flowers not on a spadix, furnished with both calyx and 

 corolla; sepals and petals each 3, distinct; ovaries numerous, distinct, 

 becoming akenes in fruit. — Eoots fibrous ; leaves radical, petiolate, 

 strongly nerved with transverse veinlets, the earlier sometimes without 

 blade; flowers in a loose raceme or panicle. 



1. Allsma. Flowers perfect. Carpels verticillate, obovate-oblong, flattened. 



2. Saglttaria. Flowers monoecious or dioecious. Carpels capitate, flattened and mem- 



branously winged. 



1. ALISMA, L. Water-Plantain. 



Petals small. Stamens 6, rarely more. Ovaries on a disk-like receptacle. 

 Akenes in a crowded whorl, somewhat channelled on the back, obtuse. — 

 Herbs in shallow water or mud, with small flowers in a verticillately branched 

 panicle. 



1. A. PlantagO, L., var. Americanum, Gray. Leaves long-petioled, 

 ovate, oblong, or lanceolate, pointed, mostly rounded or heart-shaped at the 

 base, 3 to 9-nerved : carpels obliquely obovate, forming an obtusely triangular 

 whorl in fruit. — From the base of the mountains eastward across the conti- 

 nent ; also from California to Washington. 



2. SAGITTARIA, L. Arrow-head. 



Staminate flowers above. Petals usually conspicuous. Stamens numerous, 

 rarely few. Ovaries crowded in globose heads. Akenes abruptly beaked by 

 the very short style. — Stoloniferous herbs with milky juice, broadly sheathing 

 leaves often without a blade, and mostly simple stems bearing one to few whorls 

 of flowers usually in threes. 



1. S. variabilis, Engelm. Rootstock tuberiferous : scape £ to 2 feet 

 high or more, angled : leaves very variable, ovate-sagittate, or more or less 

 narrowed, or even linear, acute, the similar lobes more or less divergent, acu- 

 minate : petals white, rounded, exceeding the sepals : fruiting heads nearly 

 half an inch in diameter : akenes obovate, with a conspicuous acute horizontal 

 beak at the upper angle. — Prom the mountains eastward across the conti- 

 nent ; also from Nevada and California to British Columbia. 



Order 86. NAIADACEjE. (Pondweed Family.) 



Marsh or mostly immersed aquatic herbs, with stems jointed and 

 leafy (naked and scape-like in Triglochin), leaves sheathing at base or 

 stipulate, and flowers perfect or unisexual, often spathaceous, with or 

 without perianth ; ovaries 1 -celled, 1-ovuled. 



