196 CACTUS FAMILY. 



1. Tube formed of the united sepals, more or less extended beyond the ovary ; stem 

 either continuous or jointed. 



* Stems or branches ^-many-angled, or grooved, or terete, and with tubercles or woolly 



tufts bearing a cluster of spines, prickles, or bristles. 

 f- Stem mostly elongated, rarely globular ; flower tube scaly. 



1. CEREUS. Stem regularly ribbed or angled lengthwise, and with the clusters of spines 



or bristles on the ridges one above the other. Flowers from the side of the stem, 

 commonly with a conspicuous tube, which, with the ovary below, is beset with scale- 

 like sepals and generally with woolly or bristly tufts in their axils. Petals numerous 

 and spreading. 



+- + Stem globular or very short ; flower tube not scaly. 



2. ECHINOCACTUS. Stem with many ribs or ridges, bearing clusters of spines one 



above the other. Flowers naked at the summit of the ridges, and with a short or 

 very short tube ; otherwise as in Cereus. 



8. MAMILLARIA. Stems mostly tufted, not ribbed, covered with distinct and strongly 

 projecting nipple-shaped tubercles, which are arranged in spiral order and tipped with 

 a cluster of prickles. Flowers from the axila of the tubercles, with a short tube. 

 Ovary and berry not scaly. 



* * Stems and branches of flat and leaf-like joints, with the margins more or less 



toothed or crenate, and with an evident woody center or midrib, with no prickles 

 and bristles, or only tufts of very short ones in the notches. 



4. EPIPHYLLUM. Joints of the branches short and truncate, very smooth, and flower- 



ing from the end. Flowers open in the daytime and for several days, mostly oblique, 

 the tube not much lengthened ; the sepals and petals rose-red, rather few, the inner- 

 most and larger ones about 8. Stamens not very many. Stigmas erect or conniving. 



5. PHTLLOCACTUS. Leaf-like branches or joints long, arising from the side of older 



ones, which with age form terete stems. Flowers from the marginal notches, slightly 

 if at all irregular. Stigmas slender and spreading. 



2. No tube to the flower above the ovary ; stem jointed. 



6. OPUNTIA. Stem branching, formed of successive joints, which are mostly flat, bearing 



at first some minute awl-shaped bodies answering to leaves, which soon fall off, and 

 tufts of barbed bristles and often prickles also in their axils. Flowers from the edge 

 or side of a joint, opening in sunshine and for more than one day. 



1. CEREUS. (Probably from Latin : wax taper or candle, from the 

 form of the stem of some species.) The following are the commonest 

 in cultivation, mostly from Mexico and S. America ; flowers summer. 



1. Stems and branches long, spreading, creeping or climbing, remotely 

 jointed more or less, only 3-7-angled, very large flowered. 



* Flower red, open in daytime for several days ; stamens much declined. 



C. speciosissimus, DC. The commonest red-flowered Cactus ; with 

 stems 2-3 high, rarely rooting, 3 or 4 broad and thin wavy-margined 

 angles or wings, and crimson or red flowers of various shades, 4'-5' in 

 diameter, the tube shorter than the petals. 



* * Flower white as to petals, opening at night, collapsing next morning, 

 fragrant, 6'-9' in diameter when expanded, the tube 4'-5' long ; stems root- 

 ing and so climbing ; prickles short and fine. NIGHT-BLOOMING CEREUS. 



C. triangu/aris, Mill., has sharply triangular stems, minute prickles, 

 and flower with glabrous tube, olive-green sepals, and yellow stamens. 



C. nycticalus, Link, has 4-6-angled stems with very minute prickles, 

 and flower much like the next, but with brownish sepals. 



C. grandiflbrus, Mill. COMMON NIGHT-BLOOMING CEREUS. Stems 

 terete, with 5-7 slight grooves and blunt angles, bearing more conspicuous 

 prickles, long bristles on the flower tube, and dull-yellow sepals. 



