THE 



GARDENER'S MAGAZINE, 



OCTOBER, 1828. 



PART I. 



ORIGINAL CORRESPONDENCE. 



Art. I. OutIz?ies of Uortiadiicral Chemistry : — Vegetable 

 Physiology. By G. W. Johnson, Esq., of Great Totham, 

 Essex. 



{Continued from p. 207.) 



X NOW proceed to consider those parts of plants which are 

 apparent above ground. These consist of the stems, branches, 

 leaves, flowei's, and fruit. 



Of the first two, it will be primarily necessary to sketch the 

 anatomy. Tho, epidermis is analogous to the human cuticle, 

 or scarf-skin, being the external envelope of the whole surface. 

 It is commonly transparent and smooth, sometimes hairy ; 

 in other instances hard and rugged, occasionally so abounding 

 with silica or flint, as to be employed as a polisher for wood 

 and even brass. In every instance it is a network of fibres, 

 the meshes of which are filled with a fine membrane. The 

 epidermis appears to be designed as a preservative from the 

 injurious effects of the atmosphere, to regulate the quantity of 

 gaseous matter and moisture respired, and as a shield from 

 the attacks of animals, &c. It is certainly devoid of sensation. 

 The texture of the membrane v/ithin the meshes varies much 

 in different species of plants. In very succulent plants, it is 

 so contrived that it readily allows the absorption of moisture, 

 but prevents perspiration. Such plants are, consequently, 

 well qualified to inhabit hot climates and dry soils. Neither is 

 it at all impossible that it possesses the quality of allowing 

 the passage of some gases, and rejecting others, as the bladder 

 of animals permits water to pass through its texture, but is 

 impervious to alcohol. In old trees it cracks, and, in many 



Vol. IV. — No. 16. y 



