THALAMIFLORiE iig 



8. The Rockrose Group. 



In the British Isles the order Cistaceae includes 

 only the Rockroses, of which there are several 

 species, and the common one has been selected as a 

 type of the order. 



There are four genera and over one hundred and 

 fifty species throughout the world, three being natives 

 of South America, the rest of the Mediterranean 

 region, South and West Europe, North Africa. 



In this group are included the Gum-Cistuses of 

 the garden. Gum Ladanum or balsam is derived 

 from Cistus creticiis. 



The Rockroses are herbaceous, or shrubby plants. 

 Many are addicted to a dry soil, with wiry stem and 

 rolled back leaves, and glandular hairs, and are 

 undershrubs. Some are calcicole or confined mainly 

 to chalk or limestone soil. 



The leaves are frequently opposite, in some exotic 

 types alternate and entire, with or without stipules. 

 In Helianthemum gnttatum there are stipules in the 

 case of the upper leaves, which are narrows-based, 

 none in the case of the lower leaves, which are broad- 

 based. The stipules thus serve to protect the buds 

 in the axils. 



The flowers are solitary, or in terminal racemes or 

 cymes. They are regular and hermaphrodite, with 

 male and female elements in the same flower. 



The calyx is polysepalous, with three or five sepals, 

 the two outer smaller than the inner, overlapping in 



