Widely distributed in moist or wet soil in Okla. (McCurtain Co.), Tex. in the 

 Coastal and Blackiand prairies and the Rio Grande Plains, and Ariz. (Cochise, 

 Pima and Maricopa cos.), Mar.-June from s. U.S. and W.I., s. to S.A.; a pan- 

 trop. weed. 



2. Apiiim graveolens L. Wild celery. Fig. 583. 



Plant perennial, erect or ascending from a taproot, not rooting at the nodes, 

 5-15 dm. high: leaves oblong to obovate, to 18 cm. long and 8 cm. wide, pinnate 

 with few pairs of ovate to suborbicular leaflets that are usually 3-lobed to near the 

 middle; cauline leaves frequently cuneate, sometimes laciniate; umbels sessile or 

 short-pedunculate, the peduncles to 12 mm. long; involucre and involucel lacking; 

 rays 7 to 16, to 25 mm. long; pedicels 1-6 mm. long; calyx teeth minute but 

 evident; carpophore shortly bifid; fruit suborbicular to ellipsoid, about 1.5 mm. 

 long, 1.5-2 mm. broad. Celeri graveolens (L.) Britt. 



A garden plant escaped from cultivation found in marshes and along streams 

 and other wet places in Ariz. (Coconino to Cochise, Pinal and Yavapai cos.) and 

 in Trans-Pecos Tex., June-July; a Euras. species widely adv. in the W. Hemis. 



14. Conium L. 



A genus of 2 species, one circumboreal in damp places, the other African. 



1. Conium maculatum L. Poison hemlock. Fig. 584. 



Plant slender, erect, glabrous, 5-30 dm. high, biennial from stout taproots, the 

 branching stems usually spotted; leaves broadly ovate, 1.5-3 dm. long, 5-30 cm. 

 broad, pinnately decompound, the ultimate divisions pinnately incised; inflores- 

 cence a compound dichasium of compound umbels, the peduncles terminal and 

 axillary; involucre of short ovate-acuminate bracts; involucel of numerous bractlets 

 like the bracts, with a conspicuous midrib, shorter than the pedicels; rays numerous, 

 subequal, 15-25 mm. long, spreading-ascending; pedicels spreading, 4-6 mm. long; 

 flowers white, the calyx teeth obsolete, the stylopodium depressed-conic; carpo- 

 phore entire; fruit broadly ovoid, 2-2.5 mm. long, about 2 mm. broad, compressed 

 laterally, glabrous, the prominent obtuse ribs undulate and crenate; oil tubes very 

 small and numerous, irregular, the seed face deeply and narrowly sulcate. 



Sporadically introd. in wet places in Okla. {Waterfall), in the s. half of Tex., 

 N.M. (Lincoln and Otero cos.) and Ariz. (Yavapai, Greenlee and Graham cos.), 

 May-Aug.; a Euras. species widely introd. throughout temp, regions in the world. 



Fatally poisonous if eaten. 



15. Perideridia Reichb. 



Slender or stout caulescent branching glabrous perennial herbs from tuberous or 

 fusiform fascicled roots; leaves ternately, pinnately or ternate-pinnately compound, 

 with linear divisions; umbels compound; involucre absent or of few to numerous 

 entire bracts; involucel of usually scarious or colored bractlets; flowers white to 

 pinkish; sepals evident; stylopodium conical or low-conical; fruit compressed later- 

 ally; ribs filiform; oil tubes 1 to 5 in the intervals, 2 to 8 on the commissure. 



An American genus of nine species, two in our area. 

 1. Fruits orbicular to suborbicular, 2-3 mm. long, the oil tubes solitary in the 



intervals; bractlets usually setaceous 1. P. Gairdneri. 



1. Fruits oblong to ovoid, 2.5-3.5 mm. long, the oil tubes 2 to 4 in the intervals; 



bractlets scarious or scarious-margined, often conspicuous 



2. P. Parishii. 



1233 



