LOASA FAMILY 575 



bracts lanceolate, crenate; sepals linear, 3 mm. long, twice as long as the hypan- 

 thium; petals yellowish, about 1 cm. long, long-clawed; blades spatulate. Desert 

 region: s Utah. L. Son. 



Family SS. CACTACEAE. Cactus Family. 



Succulent shrubby plants, usually spiny, the spines arising from small 

 hairy or bristly cushions (areolae) ; leaves usually wanting, if present, in ours 

 small and deciduous. Flowers perfect, in ours regular, solitary. Hypan- 

 thium well developed, enclosing the ovary. Sepals usually many, imbricate, 

 tlie inner often petal-like. Petals many, in two or more series. Stamens 

 numerous, in several series. Gynoecium of several united carpels; ovary 

 inferior, 1-celled, with several parietal placentae. Fruit a fleshy or rather 

 dry berry. 



Leaves evident, but small and deciduous ; flowers -mthout definite tube; seeds with a 



bony aril; steins jointed. 1. Opumia. 



Leaves wanting; flowers with a more or less deflnite tube; seeds without aril; stems not 



conspicuously jointed. 

 Flowers borne near the spine-bearing areolae. 



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



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



Plant-body usually globular or ellipsoid 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. Echinocactus. 



Flowers small; frxxit 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. CORYPIIANTHA. 



F 



1. OPtJNTIA Hill.* Prickly Pear, Cholla, Indian Fig, Tree Cactus. 



Fleshy plants with conspicuously jointed stems, the joints flat or terete. 

 Leaves scale-like, caducous, spirally arranged. Areolae axillary, usually spine- 

 bearing. Flowers lateral, arising from the upper part of some spine-bearing 

 areolae, Hypanthium bearing areolae, not produced beyond the ovary. Sepals 

 spreading, in several rows. Style cylindric; stigma 5-8-lobed. Berry more or 

 less pear-shaped, fleshy or rather dry. Seeds disk-like and flattened. Embryo 

 curved around the endosperm. 



Intemodes cyUndrical; spines covered with a delicate sheath. 



Intemodes very fleshy, turgid, easily detached. 1. O. echinocarpa, 



Intemodes less fleshy, not easily detached. 



Fuit dry; seeds angular. 2. O. acanthocarpa. 



Fruit fleshy ; seeds not angular. 



Plants tall (1 to 3 meters high); flowers red; 3. O. arborescens. 



Plants low and spreading (less than 1 meter high). , .. 



Spines yellow; flowers olive-green. 4. O. jjavisn, 



Sphaes white; flowers j-ellow. 5. O. Whipplex, 



Intemodes flat and broad; spines not covered by a sheath. 

 Pulvini not densely woolly. 



Fruit dry when mature, usually very spiny. 



Intemodes very fleshy, often terete m section, the termmal one easily break- 

 ing loose. 6. O. fragilis. ■ 

 Intemodes never terete in section, but always much broader than thick. 

 Intemodes somewhat turgid; spines very long. 7. O. rutila, 

 Intemodes flat; spines medium length. 

 Petals normally yeUow. 



Spines stout, dark brownish. 8. O. polyacantha. 



Spines weak, white. 9. O. Schueriniana. 



"Pftftls rpd 



Filaments red. ' 10. O. rhodantha. 



Filaments yellow. 11. O. xanthostemma. 



Fruit jUicy, usually naked or nearly so. • ^ , ., . 



Intemodes pubescent, always spineless. 12. O. bastlans, 



Intemodes glabrous. . , . , 



Intemodes often naked or sometimes bearing long, stout spmes. ^ 



Intemodes pale, somewhat glaucoiis. 13. O. humifusa. 



Intemodes deep green. 14. O. Greenei, 



* Key prepared by Dr. J. N. Rose. 



