AMMIACEAE 863 



11. Eryngium diffusum Torr. Biennial or perennial, glabrous. Stems 1-3 dm. 

 tall, more or less diffusely branched above or even from the base, prominently ridged : leaf- 

 blades rigid and leathery, palmately parted, the segments incised-serrate, spinose, thick- 

 margined : heads subglobose or depressed, 10-12 mm. in diameter, bristly : bracts of the 

 involucres incised-spinose, resembling the leaves, longer than the heads : bractlets lanceo- 

 late, entire, spine-tipped: fruit scaly, 1.5 mm. long, crowned with the long-tipped sepals. 



On sandy plains, Arkansas to Oklahoma, Texas and Mexico. Summer and fall. 



12. Eryngium "Wrightil A. Gray. Perennial. Stems 3-7 dm. tall, branching: 

 leaf-blades rigid, various, tiiose of basal leaves oblanceolate or spatulate, 5-15 cm. long, 

 pectinate-dentate or pinnatitid, the triangular teeth tipped with long bristles ; blades of 

 upper stem-leaves 2-4 cm. long, pinnately laciniate or pinnately parted, tlie segments 

 bristle-tipped : heads ovoid or oblong, 1€-12 mm. long : bracts of the involucres linear or 

 linear-lanceolate, entire or remotely spiny-toothed, about twice as long as the head : 

 bractlets subulate, surpassing the flowers, the terminal ones elongated : fruit 1 mm. long, 

 crowned with the ovate mucronate sepals. 



On hillsides, Texas to Arizona and Mexico. Summer. 



13. Eryngium compdctum Small. Similar to E. diffusum in habit, but smaller and 

 more slender. Stems terete or nearly so : leaf-segments pinnately incised, the margins 

 barely thickened : heads oblong or cylindric, 5-9 mm. long, slightly bristly : bracts of the 

 involucre linear, entire, mainly longer tlian tlie lieads : bractlets linear-lanceolate, entire, 

 spine-tipped : fruit scaly, about 1 mm. long, crowned with the acuminate sepals. 



In low grounds, near the lower Rio Grande, Texas. Spring. 



14. Eryngium Leavenworthii T. & G. Perennial, glabrous. Stems 3-10 dm. tall, 

 branching above : leaf-blades various, those of basal or lower stem-leaves oblanceolate, 

 spiny-toothed, 4-10 cm. long, passing into i^almately cleft or parted ones on the upper part 

 of the stem ; segments incised-pinnatifid, very spiny : heads cylindric or oblong-cylindric, 

 2.5-4 cm. long, each topped with a tuft of bractlets : bracts of the involucres rigid, incised- 

 pinnatifid, spinose, about as long as the head : bractlets 3-7 -toothed, the terminal ones 

 elongated, resembling the bracts : fruit 1 mm. long, crowned with the 3-5-toothed sepals. 



On dry prairies, Kansas to Texas. Summer and fall. 



15. Eryngium synchaetum (A. Gray) Rose. Perennial, bright green. Stems 

 slender, 3-7 dm. tall, corymbose above, often almost leafless : leaf-blades linear, 1-4 dm. 

 long, attenuate, few and shorter on the stem, the marginal bristles commonly in clusters of 

 2-4: heads 1-1.5 cm. long, oval or ovoid : bracts of the involucres lanceolate or oblong- 

 lanceolate, often toothed, shorter than the length of the head : bractlets similar to the bracts 

 but smaller and entire : fruit about 2 mm. long. 



In pine lands, Georgia to Arkansas, Florida and Texas. Spring and summer. 



16. Eryngium aquaticum L. Perennial, glaucous. Stems 3-18 dm. tall, corymbose 

 above: leaf-blades linear, often broadly so, 1-9 dm. long or shorter on the upper pai-1 of the 

 stem, remotely bristly along the margins, their bases folded around the stem : heads 

 peduncled, ovoid or subglobose, 10-20 mm. thick : bracts of the involucres lanceolate or 

 ovate-lanceolate, entire, with strong midrib and marginal nerves, shorter than the di- 

 ameter of the heads: bractlets similar, but smaller : fruit 3-4 mm. long, scaly. [£". yucca- 

 foelium Michx.] 



In low grounds or meadows, Connecticut to Minnesota, Florida and Texas. Spring to fall. 



6. CHAEROPHYLLUM L. 



Annual caulescent herbs. Leaves alternate : blades ternately decompound into often 

 delicate segments. Flowers often polygamous, in irregular compound umbels. Involucres 

 of 1-2 bracts, or mainly wanting. Involucels of several small bracts. Hypanthium trun- 

 cate. Sepals obsolete. Petals white, usually unequal, inflexed at the apex. Disk with a 

 small conic stylopodium. Fruit elongated, laterally flattened : carpels more or less distinctly 

 5-angled, the angles equally ribbed : oil-tubes solitary in the intervals and 2 in the inner 

 face. Chervil. 



Fruit sometimes contracted below the apex, but beakless : plants glabrous. 

 Mature umbels with 2-4 fruits on lax and spreading pedicels. 



Fruit less than 2 mm. broad, constricted below the apex. 1. C. procumbens. 



Fruit fully 2 mm. broad, not constricted below the apex. 2. C. Shortii. 



Mature umbels with 10-17 fruits on stout pedicels, or fruit sessile. 3. C. Texanum. 



Fruit beaked or narrowed to the apex : plants more or less pubescent. y 



Fruit with the ribs narrower than the intervals. 



Fruit pubescent. 4. C. dasycarpum. 



Fruit glabrous. 5. c. Floridanum. 



Fruit with the ribs broader than the intervals. 6. C. Teinturie.ri. 



