22 



FOUNDATIONS OF BOTANY 



1. S. variabilis, var. latifolia, Willd. BhoAd-lkaved Arrow- 

 head. Leaves very variable in size and shape, from broadly 

 sagittate to linear ; those groAving 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 moiKiecious 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 j^etioles. 

 Scape slender, usually longer than 

 the leaves, simple, weak, often pros- 

 trate in fruit ; bracts small, ovate, 

 connate at the base. Flowers monoe- 

 cious or dioecious, on long, thread- 

 like pedicels, about ^ in. wide. 

 Stamens 10-20, filaments downy. 

 Akenes nearly beakless. In ditches 

 and shallow pools.* 



Fig. 2. — Diagram of Inflorescence 

 of a Grass. 



g, sterile glumes ; Pi, a flowering glume ; 

 Pj, a scaly bract (palea) ; e, transparent 

 scales (lodicules) at tlie base of the 

 flower ; D, the flower. 



Fig. 3. — Fescue-grass (Festuca 

 pratensis). 



A, spikelet (compare Fig. 2) ; J5, a 

 flower, the lodicules in front and 

 the palea behind ; C, a lodicule ; 

 Z), ovary. 



