CISTUS 343 



necessary for some of the hybrids which do not perfect seed. They are 

 best taken in late summer, and struck in mild heat. Until planted out 

 permanently, rock roses should be grown in pots, as they suffer badly 

 from transplanting. Many of the species exude a fragrant gum, known 

 as labdanum or ladanum, from the young stems and leaves. The most 

 prolific source of this gum, which is used in perfumery and, at least at one 

 time, in medicine, is C. villosus var. creticus a rather tender shrub. It 

 is also got largely from C. ladaniferus. 



The following rough key of the species in cultivation will assist in 

 their identification : 



A. FLOWERS WHITE (PURE OR CRIMSON BLOTCHED) ; SEPALS THREE. 



1. Ladaniferus. Flowers solitary ; leaves nearly stalkless ; sepals scaly. 



2. Cyprius. Flowers in clusters ; leaves shortly stalked ; sepals scaly and hairy. 



3. Laurifolius. Flowers in clusters ; leaves stalked ; sepals hairy. 



B. FLOWERS WHITE ; SEPALS FIVE, HEART-SHAPED, WITH WELL-MARKED 



BASAL LOBES. 



4. Hirsutus. Leaves three-nerved, stalkless. 



5. Populifolius. Leaves up to 3^ ins. long ; long-stalked. 



6. Salvifolius. Leaves up to if ins. long ; stalked, pinnately nerved. 



7. Corbariensis* Hybrid between 5 and 6. 



8. F/orentinus. Hybrid between 6 and 9. 



C. FLOWERS WHITE ; SEPALS FIVE, OVATE. LEAVES THREE-NERVED, STALKLESS. 



9. Monspeliensis. Leaves not more than \ in. wide. 



10. Loreti. Petals crimson blotched at base ; leaves up to f in. wide. 



D. FLOWERS PURPLISH RED, UNBLOTCHED. 



11. Albidus. Leaves three-nerved, with flat margins ; flowers long-stalked. 



12. Crispus. Leaves three-nerved, with wavy margins ; flowers short-stalked, 



13. Villosus. Leaves pinnately veined. 



E. FLOWERS PURPLISH RED ; PETALS CRIMSON BLOTCHED. 



14. Purpureus. 



C. ALBIDUS, Linnaus. 



(Sweet's Cistineae, t. 31.) 



A compact, bushy shrub, ultimately 5 or 6 ft. high, if it survive long enough ; 

 young shoots, leaves, flower-stalks, and sepals covered with a dense, whitish 

 starry down. Leaves stalkless, oval, oblong or ovate, f to 2 ins. long, \ to f in. 

 wide, rounded or blunt at the apex, three-nerved at the base, and strongly 

 net-veined beneath. Flowers pale rosy lilac, with a patch of yellow at the 

 base of each petal, about 2| ins. across, borne on a stalk f to I in. long, and 

 crowded three to eight together in a terminal cluster. Sepals five, broadly 

 ovate, | to \ in. long. 



Native of S.W. Europe and N. Africa ; cultivated in 1640. It is one of 

 the hardier sorts, and will survive all but our hardest winters. The name 

 "albidus," it should be noted, refers to the foliage, and not to the flowers. It 

 has hybridised with and is closely allied to C. crispus, from which it differs in 

 its flat, not undulated leaves, and its comparatively long-stalked flowers 

 those of crispus being almost stalkless. 



