18 POACEAE. 



Flowers monoecious or dioecious, borne near the summit 

 of the scapes in whorls of 3's, pedicelled, the staminate 

 usually uppermost, whorls 3-bracted. Perianth seg- 

 ments 6, the outer 3 herbaceous, persistent and reflexed 

 or spreading in the pistillate flowers. Stamens numer- 

 ous, inserted on the convex receptacle; anthers 2-celled, 

 dehiscent by lateral slits. Pistillate flowers with num- 

 erous distinct 1-ovuled ovaries and small persistent 

 stigmas. Achenes densely aggregated in globose heads, 

 compressed; seeds curved; embryo horseshoe-shaped. 



1. S. latifolia Willd. Rootstock slender; scapes 0.2-1 m. high, 

 angled; leaves very variable, ovate-sagittate to linear, acute, lobes 

 more or less divergent, acuminate; flowers monoecious with the 

 lower verticils pistillate or dioecious, 2-4 mm. wide; petals white; 

 stamens numerous, 25-35; filaments glabrous; pistillate pedicels 

 shorter than the staminate; achenes broadly winged on both margins, 

 3 mm. long, with a lateral horizontal or curving beak, f-^ its length. 

 {S. variabilis Engelm.) 



Occasional on margins of ponds about Los Angeles. 



Family 9. POACEAE. Grass Family. 



Annual or perennial herbs of various habit, rarely 

 shrubs or trees. Stems (culms) generally hollow or 

 sometimes solid, the nodes closed. Leaves sheathing, 

 the sheaths usually split to the base on the side opposite 

 the blade, a scarious or cartilaginous ring (ligule) borne 

 at the base of the leaf-blade. Inflorescence spicate, 

 racemose or paniculate, consisting of spikelets composed 

 of 2-many 2-ranked imbricated bracts (glumes), the 2 

 lowest in the complete spikelet always empty, 1 or both 

 sometimes wanting. One or more of the upper glumes 

 usually contains in the axil a flower, which is usually 

 inclosed by a bract-like awnless organ called the palea, 

 placed opposite the glume with its back to the axis 

 (rachilla) of the spikelet, generally 2-keeled. Flowers 

 perfect or staminate, sometimes monoecious or dioecious, 

 subtended by 1-3, usually 2 minute hyaline scales 

 (lodicules) placed at the base of the ovary opposite the 

 palea. Stamens 1-6, usually 3 ; anthers 2-celled, versatile, 



