WATER PLANTAIN FAMILY 21 



3. ALISMACE.32. WATER PLANTAIN FAMILY 



Annual or perennial marsh herbs, usually with creeping run- 

 ners or rootstocks. Stems scape-like. Leaves long-petioled, 

 sheathing at the base ; petiole rounded ; blade nerved, netted, 

 or sometimes wanting. Flowers in racemes or panicles, bisex- 

 ual, monoecious or dioecious ; pedicels in bracted whorls. Sepals 

 3, persistent ; petals 3 or wanting. Stamens 6 or more. Ovaries 

 few or many, 1-celled, 1-seeded ; style short or none. Fruit a 

 1-seeded akene.* 



I. SAGITTARIA L 



Perennial; rootstocks mostly knobby or tuber-bearing. 

 Scapes erect or decumbent. Leaves long-petioled, sheathing 

 at the base, the blade round and netted, or wanting. Flowers 

 monoecious or dioecious, racemed in 3-bracted whorls of threes, 

 the upper flowers usually staminate. Sepals 3, persistent; 

 petals 3, withering-persistent or deciduous. Stamens few or 

 many. Ovaries in globose heads, 1-ovuled ; style short, per- 

 sistent. Fruit a subglobose head of flattened akenes.* 



1. S. latifolia Willd. BROAD-LEAVED ARROWHEAD. Leaves very 

 variable in size and shape, from broadly sagittate to linear, those 

 growing on the drier soil being usually the broader ; petioles 6-30 

 in. long. Scape smooth or slightly downy, 6-36 in. high ; bracts 

 acute. Flowers monoecious or sometimes dioecious, white, 1 in. or 

 more in width ; pedicels of the staminate flowers twice the length of 

 those of the fertile flowers. Filaments long, smooth, and slender. 

 Akenes with beak nearly horizontal. Ditches and muddy places.* 



2. S. graminea Michx. GRASS-LEAVED SAGITTARIA. Leaves 

 long-petioled, lanceolate, or elliptical, and acute at each end, 3-5- 

 nerved, or often linear, the earlier often reduced to flattened petioles. 

 Scape slender, usually longer than the leaves, simple, weak, often 

 prostrate in fruit; bracts small, ovate, connate at the base. Flowers 

 monoecious or dioecious, on long, thread-like pedicels, about in. wide. 

 Stamens 10-20, filaments downy. Akenes nearly beakless. In ditches 

 and shallow pools.* 



n. ALISMA L. 



Annual or perennial herbs. Leaves erect or floating, blades 

 prominently ribbed and netted, or even pinnately veined. 



