APETALOUS EXOGENOUS PLANTS. 471 



3-angled. Low ground. July-September. Stem 2°~3° 

 liigli ; leaves 3-5' long; spikes 1-2' long. Perennial. 



AvicuLARiA. Flowers axUlary, single or a-3 together ; stamens 8, rarely fewer ; 

 stigmas 3, nearly sessile ; achenium 3-angled ; cotyledons incumbent ; albumen 

 horny ; sheaths scarious, 2-3-parted, lacerated ; leaves small. 



P. AVicuLARE, L. Stem prostrate, diffuse, short-jointed ; 

 leaves sessile (1 J' long), oblong-linear or lanceolate, obtuse, 

 longer than the 3-cleft sheaths ; fioiuers clustered, nearly 

 sessile, greenish white, longer than the dull achenium; 

 stamens mostly 5. Waste places and along roads, common. 

 — ^Var., ERECTUM. (P. erectum, L.) Stem stouter, erect or 

 ascending, leaves larger (I'-lj-' long), oblong. With the 

 preceding. — Yar., littorale. (P. maritimum, L. ; P. 

 glaucum, Nutt.) Stem long (l°-2°), j^rostrate, rigid, 

 short-jointed; leaves small (4''-6"), oblong-linear, glau- 

 cous, the uppermost imbricated and scarcely longer than 

 the more conspicuous silvery sheaths; calyx reddish white, 

 shorter than the smooth achenium. Sea-coast sands, and 

 northward. 



EcHiNocAULON. Flowers in terminal dusters ; calyx 4r-5parted ; stamens G or8; 

 styles 2-3 ,* achenium lenticular or S-angled ; cotyledons accumbent ; stems weakt 

 branching^ armed on the angles, petioles, etc., with recui^ed prickles. 



P. SAGITTATUM, L. Leaves small, sagittate, acute, short- 

 petioled, smooth; jjedtmcles elongated, smooth; flowers 

 white, capitate ; stamens 8 ; styles 3 ; achenium 3-angled. 

 Wet places. June-October. Stem l°-3° long; leaves 

 1-2' long. Annual. 



ERIOGONUM, Michx. 



Fioiuers perfect or polygamous, surrounded by an invo- 

 lucre ; calyx deeply 6-cleft ; stamens 9 ; ovary free, 3-sided ; 

 styles 3 ; stiginas capitate ; achenium. 3-angled or 3-winged; 

 embryo straight in the axis of the albumen, or more or less 



