truncate to cuneate-truncate bases, midstem leaves larger and wider, oblong to 

 ovate-oblong or elliptical-oblong with cordate subclasping bases or lanceolate to 

 oblanceolate with cuneate-truncate bases, 2-7 cm. long, 5-30 mm. broad; upper 

 leaves smaller but similar: margins of the leaves apiculate-serrate; involucres 4-6 

 mm. high; corollas rose-purple. 



Infrequent in savannahs, ditches and low woods in s.e. Tex. (Hardin and Harris 

 COS.), summer; coastal areas, N.C. to Tex., S.L.P. and Q.Roo; W.I. 



19. Tessaria R. & P. Arrow-weed 

 American genus of 3 or 4 species, of which we have one. 



1. Tessaria sericea (Nutt.) Shinners. Fig. 753. 



Shrubs 1 m. tall or more with numerous erect branches, willowlike, gray- 

 green, with a "rank" odor; leaves alternate, simply sericeous, linear-lanceolate, 

 entire, essentially sessile, 1-6 cm. long, (2-) 3-5 (-6) mm. broad; heads crowded 

 into convex subcorymbiform aggregation 2-5 cm. across at the ends of the 

 branches; involucre campanulate, 4-5 mm. high; outer phyllaries ovate, obtuse 

 and tomentose; inner phyllaries linear, deciduous with the flowers; receptacle 

 slightly concave, naked; ray flowers absent; disk flowers very numerous, a few 

 central ones perfect but infertile (their corollas flared, purplish, 5-lobed), the 

 much more numerous outer ones pistillate and fertile (the corollas filiform, 

 4-lobed terminally); achenes of fertile flowers about 0.5 mm. long, brownish, 

 about 5-ribbed, nearly columnar or slightly flattened; pappus of infertile (sta- 

 minate. central) flowers persistent, of flattened whitish bristlelike members which 

 near the tips are discolored brownish and about twice as broad as the lower part; 

 pappus of fertile flowers white, bristlelike, persistent, not thickened nor dis- 

 colored. T. borealis T. & G., Pluchea borealis (T. & G.) Gray, P. sericea (Nutt.) 

 Cav., Poly pappus sericeus Nutt., Bertholetia sericea (Nutt.) Rydb. 



Locally abundant in river bottoms, forming dense thickets near streams in 

 the Tex. Trans-Pecos, N.M. (from Socorro Co. northw.) and Ariz, (widespread), 

 summer; Tex., N.M., Chih., Son., Ariz, and Calif. 



Reported to be a good honey plant. 



20. Iva L. Sump-weed. Marsh-elder 



Annual or perennial herbs, glabrous or pubescent; leaves alternate or opposite, 

 entire, serrate, lobed or pinnately divided; heads in a spiciform, spiciform-racemi- 

 form or paniculate arrangement, 2-8 mm. broad, containing both pistillate and 

 staminate flowers, the pistillate flowers peripheral, the staminate flowers repre- 

 senting the disk flowers in the center of the head; receptacle essentially flat, 

 paleaceous throughout; involucre hemispheric or turbinate; phyllaries 3 to 9, 

 sometimes imbricate, free or united; staminate (disk) flowers 3 to 20, their corolla 

 funnelform, 5-lobed, to 6 mm. long; peripheral pistillate flowers 1 to 9, the 

 corolla tubular, truncate, to 6 mm. long or in some species rudimentary; achenes 

 1-13 mm. long, cuneate to obovate, somewhat compressed, glabrous, resin-dotted, 

 tuberculate or pubescent at maturity. 



A North American genus of 19 species. 

 1. Plant annual; leaves ovate or subcordate, coarsely serrate and sometimes 

 lobed 3. /. xanthifolia. 



1. Plant perennial; leaves elliptic to obovate or lanceolate, never lobed (2) 



2(1). Phyllaries united to form a cup 2. /. axillaris. 



2. Phyllaries free; maritime plant 1. /. frutescens. 



1637 



