IN EXTRA-TROPICAL COUNTRIES. 291 



aliment as Pinus silvestris and nearly as much as poplars. It 

 pushes through shifting sand its spreading roots, which attain a 

 length of seventy feet. It will maintain its hold in hollows of drifts 

 where even poplars fail (Wessely). The roots are poisonous. The 

 allied R. viscosa attains a height of forty feet. No less than four 

 arborescent Robinias are recorded from Juan. Fernandez. 



Roccella tinctoria, Candolle. 



Canary Islands, Azores, also in Middle and South Europe and 

 North Africa. This Lichen furnishes the litmus, orseille or orchil 

 for dyes and chemical tests. It is a question of interest whether it 

 could be translocated and naturalised on the cliffs also of our shores. 

 Other dye-lichens might perhaps still more easily naturalised ; for 

 instance, Lecanora tartarea, L. parella, Pertusaria communis, Par- 

 melia sordida, Isidium corallinum, and some others, which furnish 

 the Cudbear or Persio. 



Rosa centifolia, Linne.* 



The Cabbage Rose. Indigenous on the Caucasus and seemingly also 

 in other parts of the Orient. In some of the German monasteries 

 real trees of this species occur, which have lived through several 

 centuries, and are regarded with sacred veneration there. Much 

 grown in South Europe and South Asia for the distillation of rose- 

 water and oil or attar of roses. No pruning is resorted to, only 

 the dead branches are removed ; the harvest is from the middle of 

 May till nearly the middle of June ; the gathering takes place 

 before sunrise (Simmonds). From 12,000 to 16,000 roses, or from 

 250 Ibs. to 300 Ibs. of rose petals, are required according to some 

 calculations for producing a single ounce of attar through ordinary 

 distillation. The flowers require to be cut just before expansion ; 

 the calyx is separated and rejected ; the remaining portions of the 

 flowers are then subjected to aqueous distillation, and the saturated 

 rose-water so obtained is repeatedly used for renewed distillation, 

 when from the overcharged water the oil separates on a cold place 

 and floats 011 the surface, from whence it can be collected after 

 refrigeration by fine birds' feathers. Rose oil consists of a hydro- 

 carbon-stearopten which is scentless, and an elaeopten which is the 

 fragrant principle. But some other methods exist for producing 

 the oil ; for instance, it may be got by distilling the rosebuds with- 

 out water at the heat of a salt water bath. The odour may also be 

 withdrawn by alcoholic distillation from the roses, or be extracted 

 by the " enfleurage " process. The latter is effected by placing the 

 flowers, collected while the weather is warm, into shallow frames 

 covered with a glass plate, on the inner side of which a pure fatty 

 substance has been thinly spread. The odour of the flowers is 

 absorbed by the adipose or oleous substance, though the blossoms 

 do not come with it in direct contact ; fresh flowers are supplied 



