156 Order LOASALES 
Internodes 7-13 cm. long; spines dissimilar, 1-8 or wanting, 
2-2.5 cm. long. 1. O. humifusa. 
Internodes 15-20 cm. long; spines alike, 3-5, 3.5-6 cm. long. 
2. O. tortispina. 
Pulvini 8-12 mm. apart, spines 8-15; fruit dry, spiny. 
3. O. polyacantha. 
Flowers red; pulvini 2—4-spined; fruit, very spiny. 4. O. rhodantha. 
Internodes terete or slightly flattened, easily breaking apart, 2-5 cm. 
long. 5. O. fragilis. 
1. Opuntia humifusa Raf. Western Prickly Pear. 
Common in dry soil in the northwestern part of the state. Belmont; 
Cherry county; Long Pine; Pine Ridge; Thomas county; Wilsonville. 
2. Opuntia tortispina Englem. 
Nebraska, according to Britton’s Manual. 
3. Opuntia polyacantha Haw. 
In dry prairies mostly in the western part of the state. Alliance; 
Belmont; Cherry county; Grand Island; Holdrege; Phelps county; 
Pine Ridge; Plummer Ford; Thedford. 
4, Opuntia rhodantha K. Sch. 
Nebraska, according to Rydberg’s Flora of Colorado. 
5. Opuntia fragilis (Nutt.) Haw. 
In dry soil in the northern and western parts of the state. Cherry 
county; Deuel county; Sheridan county; Valentine. 
LOASALES. 
Erect herbs; flowers perfect; stamens numerous. 1. Loasacez. 
Climbing or prostrate vines; flowers monecious or diccious; sta- 
mens not more than three. 2. Cucurbitacez. 
1. LOASACEA. 
1: Mentzelia. 641. 
Flowers small, not over 2 ecm. broad, petals five; capsule linear. 
1. M. albicaulis. 
Flowers larger, over 3 cm. broad; capsule oblong. 
Flowers yellowish-white, opening in the evening; capsule bracted. 
Bracts below the capsule, entire or pinnatifid; flowers 5 cm. 
broad. 2. M. nuda. 
Bracts on the capsule; flowers 10 cm. broad, mostly solitary. 
M. decapetala. 
Flowers bright yellow, opening in sunshine; capsule bractless. 
4, M. levicaulis. 
1. Mentzelia albicaulis Doug. 
Scotts Bluff. 
2. Mentzelia nuda (Pursh) T. & G. 
Dry prairies in the western part of the state. Alliance; Belmont; 
Deuel county; Dismal River; Pine Ridge; Scotts Bluff; Turner creek. 
3. Mentzelia decapetala (Pursh) Urban Gilg. 
Dry prairies mostly in the western and northern parts of the state. 
Chadron: Franklin; Grand Rapids; Hat Creek basin; Niobrara; Pine 
Ridge; Red Cloud; Scotts Bluff county. 
