CACTACE^. (CACTUS FAMILY.) 197 



1. MAMILLlRIA. Haw. 



Flowers about as long as wide, the tube campanulate or funnel-shaped. 

 Ovary often hidden between the bases of the tubercles, naked, the succulent 

 berry exserted. Seeds yellowish-brown to black, crustaceous. Globose or 

 oval plants, covered with spine-bearing cylindrical, oval, or conical tubercles, 

 the flowers from distinct woolly or bristly areoles at their base. (Name from 

 mamilla, a nipple, referring to the tubercles.) 



1. M. vivipara, Haw. Simple or cespitose, 1 - 5' high, the almost terete 

 tubercles bearing bundles of 5 - 8 reddish-brown spines (10" long or less), sur- 

 rounded by 15-20 grayish ones in a single series, all straight and very rigid; 

 flowers purple, with lance-subulate peials and fringed sepals; berry oval, 

 green , seeds pitted, light brown. Plains, Dakotas to Kan., and westward. 



2. M. Missouriensis, Sweet. Smaller, globose, with fewer (10-20) 

 weaker ash-colored spines ; flowers yellow, 1-2' broad ; berry subglobose, 

 scarlet, seeds few, black, pitted. (M. Nuttallii, Engeim.) S. Dak. to central 

 Kan., Tex., and westward. 



2. OPUNTIA, Tourn. PRICKLY PEAR. INDIAN FIG. 



Sepals and petals not united into a prolonged tube, spreading, regular, the 

 inner roundish. Berry often prickly. Seeds flat and margined, covered with 

 a white bony arillus. Embryo coiled around albumen ; cotyledons large, foli- 

 aceous in germination. Stem composed of joints (flattened in ours), bearing 

 very small awl-shaped and usually deciduous leaves arranged in a spiral order, 

 with clusters of barbed bristles and often spines also in their axils. Flowers 

 in our species yellow, opening in sunshine for more than one day. (A name 

 of Theophrastus, originally belonging to some different plant.) 

 # Spines small or none ; fruit pulpy. 



1 . O. VUlgaris, Mill. Prostrate or spreading, light green ; joints broadly 

 obovate (2 - 4'' long) ; leaves minute (2 - 2|" long), ovate-subulate, generally ap- 

 pressed ; bristles short, greenish yellow, rarely with a few small spines ; flowers 

 pale yellow (about 2' broad), with about 8 petals; fruit 1' long. Sandy fields 

 and dry rocks, Nantucket to S. C., near the coast; Falls of the Potomac. 



2. O. Raflnesquii, Engeim. Prostrate, deep green ; joints broadly obo- 

 vate or orbicular (3-5' long) ; leaves (3-4" long), spreading ; bristles bright 

 red-brown, with a few small spines and a single strong one (9-12" long) or 

 none; flowers yellow (2-3-^ broad), sometimes with a reddish centre; petals 

 10-12; fruit 1|' long, with an attenuated base. Sterile soil, Nantucket and 

 southward along the coast to Fla., and in the Mississippi valley, from Mich, to 

 Minn., and south to Ky. and Ark. 



* # Very spiny , fruit dry and prickly. 



3. O. Missouriensis, DC. Prostrate , joints light green, broadly obo- 

 vate, flat and tuberculate (2 -6' long), leaves small (l-2" long) ; their axils 

 armed with a tuft of straw-colored bristles and 5-10 slender radiating spines 

 (1 - 2' long) ; flowers light yellow (2 - 3' broad) , fruit with spines of variable 

 length. Wise, to Mo., westward across the plains ., very variable. 



4. O. fragilis, Haw, Subdecumbent ; joints small (1-2' long or less), 

 ovate, compressed or tumid, or even terete ; leaves hardly 1 " long, red ; bristles 



