7. Triglochidiatus, K. Sch

(E. triglochidiatus, Engelm. Cereus triglochidiatus, Engelm.). Radial spines usually 3, sometimes as many as 6, strong, angled, base bulbose, straight or curved, about 1 in. long, soon ash-gray. Texas and New Mex.

dd. Ribs 9-11. E. Axils of flower-bracts filled with long cobwebby hairs.

8. Polyacanthus, Engelm

(Cereus polyacanthus, Engelm.). stems clustered, forming thick masses, cylindrical to ellipsoidal: ribs 9-13: radial spines 8-12, robust, subulate, stiff and sharp, under one the longest, nearly 1 in., upper ones scarcely 1/2in., white to reddish gray with dark tips; centrals 3-4, bulbose base, stronger, about the length of the radials or the lowest sometimes reaching 2 in., horn-colored; later all the spines become gray: flowers lateral, about 13/4-2 1/4 in. long, dark scarlet to blood-red: fruit spherical, about 1 in. long, greenish red, spiny. Texas to N. Mex.

ee. Axils of flower-bracts bearing short wool. p. Central spines always solitary: stems 6-8 in. high. Mex.

9. Acifer, Lem

(Cereus acifer, Otto). stems thickly clustered, 6-8 in. high by 1 1/2-2 in. diam., becoming gray and corky with age: ribs 9-11, usually 10: radial spines usually 9, spreading, under pair longest, about 1/2in., in young growth white, later horn-colored to gray, the upper ones brownish; central solitary, straight, porrect, at first ruby-red, later brown, 1 in. long: flowers lateral, 2 in. and more long, clear scarlet-red, with a yellow throat and sometimes a carmine border. N. Mex.

fp. Central spines 1-4: stems 2-4 in. high. New Mex. and Colo.

10. Coccineus, Engelm

(E. phceniceus, Leva. Cereus phceniceus, Engelm.). stems irregularly clustered, ellipsoidal to short-cylindrical, 2-4 in. high by 1 1/2-2 1/4 in. diam.: ribs 8-11, straight: spines bristle-form, straight, round; radials 8-12, white, 1/4-1/2 in. long, upper ones shortest; centrals 1-4, stouter, white to yellow or brown, with bulbose base: flowers from upper lateral areoles scarlet-red, with the corolla-throat yellow. Colo, to Ariz.

Variety conoideus, Engelm. (E. conoideus, Rumpl Cereus conoideus, Engelm.). Central spine long and robust: flowers large, red. S. Calif, and N. W. Mex.

cc. Flowers never scarlet, usually crimson or purplish, sometimes yellow.

d. Spines more or less pectinate: ribs 12 or more.

e. Areoles short, nearly orbicular.

f. Color of spines white.

11. Longisetus, Lem

(Cereus longisetus, Engelm.). stems clustered, cylindrical, covered with long, dirty white spines, about 8 in. high by 2 in. diam., light green: ribs 11-14, straight, undulate: radial spines 18-20, straight, compressed, base thickened, subulate, flexuose, usually horizontally spreading, interlocking with adjacent clusters, the lower laterals the longest, reaching 3/8in. long, the upper more bristlelike and the. shortest, all white; centrals 5-7, longer, reaching 2 1/2 in., stronger, the upper ones scarcely longer than the longest radials; all are bulbose at the base; the 3 lower ones the longest and deflexed, spreading and sometimes curved: flowers red. Mex.

ff. Color of spines white and brown. 12. chloranthus, Rumpl. (Cereus chloranthus, Engelm.) Fig. 1375. stems in small clusters, cylindrical, slightly tapering above, 4-9 in. high by 2-2 1/2 in. diam.: ribs 13-18, straight or rarely spiral: radial spines 12-20, horizontally spreading and ap-pressed, sharp, the shortest one about 3/8in. long and white, the lower laterals a little longer and have purple tips; centrals 3-5, or in young plants absent, bulbose at the base, the upper ones shortest, about the length of the radials, and darker colored, with purplish tips, the lower ones stouter, about 1 in. long, deflexed, white; frequently all the spines are white: flowers lateral, little more than 1 in. long; ovary and tube white bristly; petals green: fruit ellipsoidal, about 1/2in. long, spiny. Texas and New Mex.

Echinocereus chloranthus.

Fig. 1375. Echinocereus chloranthus.

ee. Areoles more or less elongated.

f. Color of flowers greenish or yellow.

G. Flowers greenish.

13. Viridiflorus, Engelm

(Cereus viridiflorus, Engelm.). stems solitary or only in age forming small, loose clusters, cylindrical or elongated, ellipsoidal, 3-7 in. high by 1-2 in. diam: ribs 13: radial spines 12-18, horizontally radiate, pectinate, straight or somewhat curved, subulate, the lower laterals the longest, about 1/2in., translucent ruby-red, the others white; centrals usually absent, rarely 1, strong, about 3/4in. long, curved upward, red with brown point: flowers lateral, from just below the crown, broad funnelform, little more than 1 in. long; ovary and tube spiny; corolla green, with a broad darker olive-green to pink stripe down the middle of each petal: fruit ellipsoidal, about 1/2in. long, greenish. Wyo. and Kans. to Texas and New Mex.

gg. Flowers yellow.

H. Ribs 15-21: central spines unequal.

14. Dasyacanthus, Engelm

(Cereus dasyacanthus, Engelm.). stems solitary or sometimes forming open clusters, ellipsoidal to short-cylindrical ribs 15-21, straight or sometimes slightly spiral, obtuse: radial spines 20-30, straight or sometimes slightly curved, subulate, stiff, sharp, pectinate, white with red or brown tips, later gray, the laterals longest, 1/2-l in., the upper ones shortest, about 3/8in., those of one cluster interlocking with those of the adjacent clusters; centrals 3-8, the lower one longest, white with colored tips, mostly with bulbose bases: flowers from near the crown of the stem large, 2 1/2-3 in. long; ovary and short tube covered with white, reddish tipped stiff bristles; corolla yellow: fruit 1-1 1/2 in. long, ellipsoidal, spiny, green to reddish. Texas.

hh. Ribs 15 or 16: central spines very short, equal.