1. Perideridia Gairdneri (Hook. & Am.) Mathias. 



Plants slender, to 12 dm. high, from a solitary fusiform tuber or a small fascicle 

 of tubers; leaf divisions to 15 cm. long, entire or toothed; involucre absent or of 

 one to several setaceous bracts; rays 8 to 20, to 6 cm. long; fruit 2-3 mm. long. 



Wet heavy soil, in Ariz. (Apache, Coconino and Navajo cos.) and N. M. 

 (Socorro Co.); B. C, Wash., to s. Calif., e. to Alta. and N. M.; June-Aug. 



2. Perideridia Parishii (Coult. & Rose) Nels. & Macbr. 



Plants slender, to 8 dm. tall, from a solitary tuber or a fascicle of fusiform or 

 ovoid tubers; leaves ternate, or sometimes simple or biternate, the leaflets to 10 cm. 

 long, the terminal often elongate; involucre usually absent; rays 8 to 15, unequal, 

 to 4 cm. long; bractlets conspicuous, scarious or colored; fruit 2.5-3.5 mm. long. 



Usually in moist or wet meadows or moist soil in pine woods, in Ariz. (Coconino 

 Co.) ; Calif., Nev. and n. Ariz. 



16. Berula Hoffm. Water-parsnip 

 A genus of two species, one circumboreal, the other African. 



1. Berula erecta (Huds.) Cov. Fig. 585. 



Plants slender, erect, stoloniferous, perennial from fascicled fibrous roots, 2-8 

 dm. high; leaves narrowly oblong, to 3 dm. long and 1 dm. wide, pinnate; leaflets 

 oblong, distinct, subentire to serrate or lobed, those of the submerged leaves decom- 

 pound; cauline leaves reduced, the leaflets often linear; inflorescence of compound 

 umbels; peduncles terminal and axillary, 2-8 cm. long; involucre of 6 to 8 linear 

 to lanceolate unequal foliaceous scarious-margined entire to incisely toothed bracts, 

 5-15 mm. long; involucel of 4 to 8 linear to lanceolate acute entire bractlets, 1-5 

 mm. long; rays 6 to 15, subequal, spreading-ascending, 1-2 cm. long; pedicels 2-5 

 mm. long; flowers white, the minute calyx teeth subulate, the stylopodium conic; 

 carpophore divided to the base, the halves wholly adnate to the mericarps; fruit 

 oval to orbicular, 1.5-2 mm. long, compressed laterally, the filiform ribs obscure 

 in the thick corky pericarp; oil tubes numerous about the seed, the seed face plane; 

 strengthening cells lacking. B. pusilla (Nutt.) Fern. 



In marshes, streams, seeping banks, edge of ponds and wet places in Okla. 

 (Alfalfa, Woods and Major cos.), Tex. in the Blackland Prairies, Plains Country 

 and Trans-Pecos, N. M. (widespread), Ariz. (Apache to Coconino and Yavapai, 

 s. to Santa Cruz and Cochise cos.), May-Nov.; throughout the U.S. and adj. Can.. 

 s. to Guat.; also Eur. and the Medit region. 



17. Sium L. Water-parsnip 



A chiefly circumboreal genus, containing perhaps a dozen species. 



1. Sium suave Walt. Fig. 586. 



Plant stout, perennial, 6-12 dm. high, the corrugated branching stems arising 

 from fusiform fascicled roots; leaves oblong to ovate, to 25 cm. long and 18 cm. 

 wide, pinnate or rarely simple and serrate and incised, the submerged leaves usually 

 decompound; leaflets lanceolate to linear, 1-4 cm. long, 3-15 mm. wide, distinct, 

 remote, the lower frequently obsolete, finely to coarsely serrate or incised; pedun- 

 cles stout, 4-10 cm. long; involucre of 6 to 10 lanceolate or linear bracts 3-15 mm. 

 long that are acute, entire or incised, unequal and reflexed; involucel of 4 to 8 

 linear-lanceolate bractlets 1-3 mm. long, acute, entire; rays 10 to 20, slender, sub- 

 equal, 1.5-3 cm. long; pedicels 3-5 mm. long; flowers white; calyx teeth minute, 

 the stylopodium usually depressed; the halves of the carpophore adnate to the 

 mericarps; fruit oval to orbicular, 2-3 mm. long, 2-2.5 mm. broad, slightly com- 

 pressed laterally and constricted at the commissure, the ribs prominent, subequal, 



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