290 



CACTACEAE (CACTUS FAMILY) 



short, grayish-white bristles, becoming stiff and straw-colored as 

 the plants grow old, with usually about four stouter, yellowish- 

 brown spines, a half-inch to an inch long. Flowers pale yellow, 

 nearly two inches broad. Fruit ovate, inedible, prickly, becoming 

 dry at maturity. Seed rather large and thick, with a corky margin. 

 Means of control the same as for the preceding species. 



GLOBE CACTUS 



Mamillaria vivipara, Haw. 



Other English names: Ball Cactus, Purple Cactus. 



Native. Perennial. Propagates by seeds. 



Time of bloom : June to July. 



Seed-time: Early in the following summer. 



Range : Manitoba to Alberta, southward to Kansas, Colorado, and 



Utah. 

 Habitat : Dry soil ; prairies, rocky hillsides, pastures. 



When these small spiny plants occur in pasture land, they are 

 most unpleasant weeds, occupying the place of forage too scanty at 

 best. This species usually grows in tufts, forming 

 large flat masses. Stems two to four inches in 

 diameter, usually depressed globose, covered with 

 fleshy, rather loose, slightly grooved, nearly cylindri- 

 cal green tubercles, woolly at base, each bearing a 

 central bundle of four to eight reddish brown spines, 

 a half-inch or more long, erect or somewhat spread- 

 ing, surrounded by fifteen to twenty smaller, radi- 

 ating, grayish-white spines in a single row. Flowers 

 solitary, growing from small cavities at the base of 

 the tubercles, funnel-shaped, nearly two inches long 

 and about as wide when fully open (which is only 

 for a few hours in bright sunlight) with fringed 

 Ball or Globe sepals and narrow, lance-shaped petals, deep purple ; 

 miitarL ^riri stamens verv numerous and style divided into thread- 

 para), x i-. ^ke, stigmatic branches ; ovary inferior, one-celled. 

 Fruit a little more than a half-inch long, ovoid, 

 pale green, juicy ; seed about a twelfth of an inch long, obovoid, 

 slightly curved, light brown, the surface finely pitted. (Fig. 203.) 



FIG. 203. 



