16S Esplanalion of the Cuticle of Leaves. 



kiiKi, which I douht not has often deceived botanists, and been 

 taken for perspiration ; whereas it is so perfectly without mois- 

 ture, that the longer the leaves are kept within, and the mors 

 they are dried np, the more shining and brilliant it is. The 

 yellow azaiui will live and do well ont of bog earth ; but I be- 

 lieve the others almost always lin.ger and die away. The cuticle 

 of the leaves of the yelloiu azalia differs much, especially one 

 always growing in common earth : but as I keep the variation to 

 be discovered by a change of situation and soil, for my second 

 letter, I shall not anticipate it here, except by saying that it has 

 more hairs, and not so thick a pabulum, nor are the leaves so 

 generally rigid. 



I shall now turn to the rock plant, one of the most cmious of 

 all, as drawing hardly any nourishment from the earth. It is the 

 only plant formed without the impervious shiv, and has there- 

 fore millions of mouths open in every leaf ready to suck in the 

 moisture of the atmosphere. The upper cuticle is entirely com- 

 /)o.ve(Z of diminutive round swellings; and these are full oi points, 

 which absori) the moisture by means of the vacuum managed 

 within ; and the cuticle, ])cing at some distance from the pabu- 

 lum, is nothing but plain water, confined in skins with each a 

 pore that opens and closes, cotitracied by the spiral luire. Real 

 rock plants have no hairs. Used to live in alpine situations, on 

 the Table mountain of the Cape, or on some high rocks, where 

 the atmosphere is constantly bestowing vapour which feed and 

 bathe them, they scarcely want the little ajjpendage that often 

 belongs to the minor ones, which creep over the rocks, and seek 

 the little cavities of the stones. This is a small kind of pump, 

 something like that which belongs to parasite plants : it seems 

 merely intended to keep the root-stems moist, for the running- 

 up of the seeds. All the leaves are very thick and succulent ; 

 two cuticles above and the same below, but most of the leaves 

 flat on one side ; they have (like all other plants) hairs when 

 young. The ice plant is not a pro])ej- epitome of a rock plant, 

 because it has its pabulum at the exterior of the outward cu- 

 ticle, instead of the middle of it. But most of the ledums are 

 so, and many of tlje sa.riJ'rn^Q<; and sempcrviuums; the drala 

 acyoides, enH//y rt/pi/;«s, and innumerable others: most of these 

 would soon die, if deprived of the moisture of the atmosphere. 

 Though these plants have few if any hairs, yet they have points 

 of various kinds which produce the same effects; that is, be- 

 stowing on the plant those peculiar juices without which it can- 

 not be supported. To receive these oils and li<iuids is a very 

 different matter from gaining siistevance fiom the leaves : nor 

 can the diiseCtor mistake them, as the colour alone, as well as 



the 



