SUCCULENT PLANTS. 



461 



Cambridge. The old Lcpismium commune is now B. Mittleri. Pfciffcra 

 cereiformis is Bhipsalis cereiformis. Brazil appears to be the head- 

 quarters of the genus. 



Opuntia. — This genus is usually recognised at once by its flat-jointed 

 stems and flowers without a tube, but a few species like 0. arborescms, 

 0. cylindrica, and 0. subulata have round stems. The flat joints, 

 however (in 0. dccumana 20 inches long by 12 inches broad), are very 

 characteristic, and are usually furnished with tufts of spines, each of 

 which very frequently has a barbed point. In 0. tunicata the spines 

 are covered with a white papery sheath, easily pulled off. 0. co chine I Lifer a 

 ("Bot. Mag.," 2742) was formerly important as the chief kind used for 

 the support of the cochineal insect. It is one of several species by 



Fig. 78. — Opuntia cantamugiensi.s at ( 



Hooker and Bentham and by Schumann held to form the genus Nopalea. 

 The stamens are much longer than in other Opuntias, but there is hardly 

 any other difference. 0. Ficus indica is the 'Prickly Pear,' fruits of 

 which are frequently imported. The genus appears to be native over 

 the entire range of the order in the New World. 



Pterocactus. — This is an interesting genus established by K. Schu- 

 mann * as a plant closely allied to Opuntia, but with dry instead of fleshy 

 fruit and a broadly winged seed. The one species is P. Kuntzei, a caespi- 

 tose plant with short clavate branches bearing yellow flowers. It is a 

 native of the Argentine Andes. 



Pereskia. — This is the one genus of Cactaceae which has leaves of the 

 ordinary type with well-developed blades. The best-known species are 

 P. aculeata and P. Bleo, both largely used as stocks for Epiphyllum. 



* Monographic, p. 753. 



