CACTUS FAMILY 579 



7. E. goniacanthus (Engelm.) Lem. Stems ovoid, 7.5-12.5 cm. high, 



simple or sparingly bnuiched at the base; ribs 7, rarely 8 or 9, tuVjerculate ; spines 

 stout, angular, straight, or curved; radials 8, the lower 16-24 mm. long, the rest 

 2-3 cm. long, yellow at the base and dark-tipped, the upper one and the solitary 

 central one stout, (J-7-angled, 3-6 cm. long, 2 mm. broarl; flowers scarlet, about 

 6 mm. long. Crrcus goniacaDthusEn^elra. Sandy hills: Colo. — N.M. Submoni. 



8. E. paucispinus (Engelm.) Rumpl. Stem ovoid or ovoid-cylindric, 12- 

 25 cm. high, 5-10 cm. thick, simple or somewhat branched, deep green; ribs 

 5-7, tubercled; spines stout, with a bulbose base, straight or somewhat curved; 

 radials 3-7, reddish or dark, at last blackish, 18-32 mm. long; central one wanting 

 or rarely a stout subangular one, 3-4 cm. long, porrect; flowers purplish red, 

 2.5-3 cm. broad. Cereus paucispinus Engelm. Rocks and limestone hills: 

 Tex.— Colo.— N.M. Submont. 



3. ECHINOCACTUS Link & Otto. Hedgehog Cactus, 

 Barrel Cactus. 



Fleshy plants, with globular, or oblong, or sometimes cylindric stems, with 

 spine-bearing ribs, or these divided into spiral or vertical rows of tubercles. 

 Leaves none. Flowers borne just above young spine-bearing areolae, hence 

 appearing almost terminal on the stem. Hypanthiiun produced beyond the 

 ovary, more or less scaly, not spiny. Style columnar; stigmas slender. Fruit a 

 fleshy or dry berry, scaly. Seeds smooth, or nearly so, with an endosperm; 

 embryo curved. 



Stem with definite ridges, not tuberculate. 



Scales of the h>ypanthium subulate, copiously wooUy in their axils; fruit dry and 

 clothed with wool. 

 Uppermost central spine the broadest; ribs of the stem 15-20. 



1. E. polycephalus. 

 Lowermost central spine the broadest; ribs of the stem 13. 2. E. leranlhrmoides. 

 Scales of the hjiiantliiuni ovate, orbicular, or cordate, not woolly in their axils; fruit 

 not woolly. 

 One or more of the central spines strongly hooked, neither armulate nor strongly 

 compressed. 

 Central spines except the hooked one, flattened, glabrous. 



3. E. Whipplei. 

 Central spines all terete, pubescent. 4. E. pubispinus. 



One or more of the central spines distinctly annular, strongly broadened, flattened 

 above, slightly if at all hooked. 

 Radial spines 9-13; upper central spine angled. 5. E. cylindraceus. 



Radial spines over 20; upper three spines terete. 6. E. Wislizeni. 



Stem with the ribs more or less divided into tubercles. 

 Tubercles terete. 



Radial spines 8-9; central ones 1-3; tubercles 1 cm. high. 7. E. subglaucus. 

 Radial spines 10-14; central spines 4; tubercles low. 8. E. Johnsoni. 



Tubercles rhombic in cross-section; radial spines 13-15. 9. E. Sileri. 



1. E. polycephalus Engelm. & Bigel. Globose to ovate or cylindric, 15-70 

 cm. high, 12.5-25 cm. in diameter, branched at the base; ribs 15-21; spines 

 8-15, very stout, compressed, more or less recurved, reddish; radials 4r-ll, com- 

 paratively slender, 2.5-5 cm. long; centrals 4, very unequal, 2-9 cm. long, the 

 uppermost broadest, curved upward, the lower longest and decurved; flowers 

 yeUow; fruit globose, 15-20 mm. in diameter. Stony or gravelly ground: Ariz. 

 — Utah — s Calif. L. Son. 



2. E. xeranthemoides Engelm. Stem globose, 2.5-12.5 cm. high; ribs 13, 

 sharp and interrujjted; spines 10-15, straight or slightly curved; radials small, 

 about 3 cm. long; centrals 4, slender, 3-5 cm. long, the lowest broadest and por- 

 rect, otherwise as the preceding. Desert regions: s Utah — Ariz. L. Son. 



3. E. Whipplei Engelm. Stem globose-ellipsoid, 7-13 cm. high, 5-10 cm. 

 thick; ribs 13-15, compressed and somewhat interrupted; radial spines 7-11, 

 white or the lower dusky, 12-36 mm. long; central spines 4, the uppermost 

 flattened, straight, 2.5^ cm. long, 1-2.5 mm. broad at base, turned upwards, the 

 others 2. .5-3 cm. long, 4-angled, dark brown, the lateral straight, the lowest sharply 

 hooked downward : flowers greenish red, 2-3 cm. long. Sandy soil: Utah — Colo. 

 — Ariz. Son. 



