326 CACTACEAE ^CACTUS FAMILY) 



lived perennial; scarcely different from the species. (M. densa Greene, Pitt. 

 3: 99. 1900.) Southern Colorado. 



10. Mentzelia laevicaulis (Dougl.) T. & G. Fl. N. A. 1: 533. 1840. Stout, 

 6-9 dm. high, branching: leaves lanceolate, 5-20 cm. long: flowers sessile on 

 short branchlets, very large, light yellow, opening in sunshine: calyx-tube 

 naked, the lobes 24-30 mm. long: petals acute at each end, 5-7 cm. long, the 

 filaments and slender style a little shorter: capsule 30 mm. long, 6-8 mm. in 

 diameter: seeds very minutely tuberculate. Wyoming and Montana to the 

 Pacific States. 



11. Mentzelia speciosa Osterh. Bull. Torr. Bot. Club 28: 689. 1901. Per- 

 ennial, finely pubescent, glandular on the pedicels and ovary, corymbosely 

 branched from near the base: the leaves linear to oblong, sinuate-dentate to 

 sinuate-pinnatifid, the lower, including the narrowly winged petiole, 10-15 cm. 

 long, hispid on both sides: flowers yellow, numerous, vespertine, the earlier 

 ones sessile, the others on pedicels 1-2 cm. long: petals 10, the 5 outer ones 

 whitish on the outside, 2 cm. long and 8 mm. wide at the widest portion, 

 narrowed to a claw which is nearly half the length of the whole petal; the 5 

 inrier ones narrow and not more than half the size of the outer, a number of 

 the outer filaments also petaloid: the capsule a little more than 2 cm. long, 

 striate: the seeds round, winged, mature ones smooth, i. e., not punctate. 

 (M. sinuata Rydb. 1. c. 566.) Colorado. 



12. Mentzelia pumila Nutt. T. & G. 1. c. Stems 2-3 dm. high, rough with 

 a 'minute barbed pubescence, whitish, branching towards the summit: leaves 

 lanceolate, sinuate, toothed, or pinnatifid, the lower ones petioled, the upper 

 sessile: flowers solitary or three together, terminating the loose flowering 

 branches, slightly pedicellate, with one or two linear-setaceous bracts at the 

 base: petals 10, lanceolate, acute, spreading, longer than the lanceolate- 

 subulate calyx-lobes, the inner ones smaller: stamens very numerous, the 

 outer filaments flat and somewhat dilated: capsule clavate-cylindrical, 3- 

 valved: seeds numerous, winged. Colorado. 



12a. Mentzelia pumila multicaulis (Osterh.) A. Nels. Leaves all narrow, 

 the upper entire: stem glabrate below: seeds scarcely winged. (T outer ea mul- 

 ticaulis Osterh. Bull. Torr. Bot. Club 30: 236. 1903.) Wolcott, Colorado. 



78. CACTACEAE Lindl. CACTUS FAMILY 



Green, fleshy, and thickened, persistent, mostly leafless plants, of peculiar 

 aspect. Globular or columnar, tuberculated or ribbed, or jointed and often 

 flattened, usually armed with bundles of spines from areolae. Flowers with 

 numerous sepals, petals, and stamens, usually in many rows, the cohering 

 bases of all of which coat the inferior, 1-celled, many-ovuled ovary, and above 

 it form a tube or cup nectariferous at base. Style 1, with several or numer- 

 ous stigmas. Fruit a pulpy or rarely dry 1-celled berry. 



Stems globose, oval or ovoid, usually not jointed; leaves wanting; spines 



not barbed. 



Flowers from between the tubercles; ovary naked . . . .1. Mamillaria. 

 Flowers from the tubercles or the ribs; ovary scaly (the imbricated 



sepals). 

 Flowers nearly terminal, arising near the young or just forming 



areolae 2. Echinocactus. 



Flowers lateral, arising near the older spine-bearing areolae . . 3. Echinocereus. 

 Stems flat or cylindrical and conspicuously jointed; leaves small, early 



deciduous; bristles barbed 4. Opuntia. 



1. MAMILLARIA Haw. BALL CACTUS 



Small, more or less globose or oval, simple or caespitose plants, the spine- 

 bearing areolae borne on cylindric, oval, conical, or angular tubercles which 

 cover the body of the plant. Flowers about as long as wide, the tube cam- 



