158 LOASACEAE 



Leaves divided to near the midrib into linear-oblong or narrowly 



lanceolate lobes. 10. .V. laciniata. 



I^eaves sinuate or lobed halfway to the midrib; lobes triangular or 

 ovate. 

 Stem erect; leaves tapering at the base, lobed. 



11. .V. sprciosa. 

 Stem decumbent at the base: leaves, at least the upper ones, 

 rounded at the base, sinuate. 12. N. crysantha. 



Petals straw-colored, usually more than 2 cm. long. 

 Outer filaments dilated; petals 2-3 cm. long. 



Petals about 2 cm. long; upper leaves with broad bases, long-acuminate. 



13. X. Rusbyi. 

 Petals nearly 3 cm. long ; none of the leaves broad at the base. 



Plant branched below; flowers subtended by sohtary entire bracts. 



14. \. nuda. 

 Plant simple below; flowers subtended by several toothed bracts. 



15. \. stricla. 

 Filaments all filiform; petals 4-5 cm. long. 16. N. decapclala. 



Petal-like staminodia none; petals 5, yellow; a few of the outer filaments shghtly dilated. 

 Stem glabrous or nearly so, white and sluning; upper stem-leaves neither with a broad 



base, nor long-acuminate. 17. N. laevicaulis. 



Stem pubescent throughout, straw-colored, rather dull; upper stem-leaves long- 

 acuminate and with a broad base. 

 Petals 5-7 cm. long; leaves coarsely liirsute-scabrous. 18. N. acuminata. 



Petals 2.5-3 cm. long; leaves finely scabroiis-puberulent. 19. N. varviflora. 



3. ACROLASIA Presl. 



Inflorescence congested; bracts broad, 3-lobed, membranous at the base. 



1. A. congesta. 

 Inflorescence open; bracts neither 3-lobed nor membranous. 



Seeds rather strongly muricate; upper leaves narrow; sepals lanceolate-subulate, half 

 as long as the petals or longer. 

 Petals 3-6 mm. long. 



Leaves pinnatifld with many lobes; petals 5-6 mm. long. 



Leaves divided to near the midrib, with ascending lobes; plant erect. 



2. A. gracilis. 

 Leaves divided one-lialf or one-third to the midrib, with divergent lobes; 



plant ascending or diffuse. 3. A. ctenophora. 



Only the middle leaves pinnatifld with few lobes, or seldom all entire; petals 

 3—4 mm. long. 4. A. albicaulis. 



Petals 2-3 mm. long; plant very slender. 



Leaves deeply pinnatifld, with narrow lobes. 5. A. Tweedyi. 



Leaves narrowly hnear, entire. 6. A. tenerrima. 



Seeds minutely muricate (tubercles seen only imder strong magnification) ; at least 

 the upper leaves broadly ovate. 

 Petals 5 mm. long; sepals about half as long, lanceolate, acute; plant tall and 



stout. 7. A. lalifolia. 



Petals 3-4 mm. long; sepals linear, obtuse, only one-tliird as long as the petals. 

 Plant tall, 3-5 dm. high; capsules 2-3 cm. long; lower leaves lanceolate or 



linear, some of them usually toothed. 8. A. dispersa. 



Plant low, less than 2 dm. lugh; capsule 12-15 mm. long; leaves all ovate, 

 entire. 9. A. compacta. 



4. MENTZELIA (Plum.) L. Stick-leaf. l. M. oligosperma. 



5. EUCNIDE Zucc. l. E. urens. 



6. PETALONYX A. Gray. 



Leaves of the branches reduced, less than 1 cm. long. 1. P. Thurbcri. 



Leaves of the branches not reduced, about 2 cm. long. 2. P. Parryi. 



Family 88. CACTACEAE. Cactus Family. 



Leaves evident, but small and deciduous; flowers without definite tube; seeds with a 



bony aril; stems jointed. 1. Opuxtia. 



Leaves wanting; flowers with a more or le-ss definite tube; seeds without aril; stems not 

 conspicuously jointed. 

 Flowers borne near the spine-bearing areolae. 



Plant-body more or less cyUndric ; spines arranged on definite ribs ; flowers arising 



from near fully developed areolae, hence lateral on the stem. 2. Echinocereus. 



Plant-body usually globular or elhpsoid or short cylindric; fruit not spiny; stem 



tubercled or ribbed, if ribbed the flowers arising near young areolae. 



hence nearly terminal on the stem. 



Flowers large; fruit covered with bracts; seeds smooth. 3. Echixocactus. 



Flowers small; fruit naked or nearly so; seeds roughened; stems tubercled. 



4. Pediocactus. 

 Flowers borne remote from the spines, at the base of the tubercles of the stem. 



5. CORYPHANTHA. 



