HARDY CACTI 371 



numerous spines, and bright purple handsome flowers. It is 

 one of the most distinct and desirable of the Alpine Opuntias, 

 and thrives best in poor sandy soil. O. echinocarpa, although 

 without showy flowers, which are of a quiet greenish yellow, 

 is sufficiently attractive for the Cacti garden through its silky 

 white centred spines. It is about a foot high, and comes from 

 the plains and mountains of Colorado and Arizona. None of 

 the Opuntias suffer from drought, but succumb in winter to 

 the damp unless covered with glass. 



Cereus. This family is quite distinct from the Opuntia, 

 the succulent plants being usually columnar, short or tall, 

 often ribbed or angled, with bundles of spines or bristles on 

 the ribs. The flowers usually open in sunlight, but close 

 when the weather is dull. O. Engelmanni is one of the best 

 known. It has white spines and large, handsome, deep purple 

 flowers in June, whilst it is found in the Western States of 

 North America. C. Emoryi is cylindrical, with straight yellow 

 spines and clusters of flowers on one side of the tip of 

 the stems. 



Mamillaria. This group is distinguished by succulent glo- 

 bose stems and small flowers. M. arizonica has large and 

 showy deep rose-coloured flowers. It has long and straight 

 spines, the exterior ones white and the few inner ones deep 

 brown. M. setispina has white spines and rose-coloured 

 flowers. 



Echinocactus cylindraceus is a handsome Cactus with red- 

 dish spines and small greenish-coloured flowers. This group 

 is quite as easily managed as any of the others, but dislikes 

 winter damp. 



Echinocereus group greatly resembles the Cereus and the 

 Echinocactus ; in fact, there is only a thin line between the 

 two families. One of the best known is E. Fendleri, which has 

 large magenta-red flowers. 



