THE SKIN OF THE APPLE AND PEAR. 



41 



points studding the skin, as in Yates, where the cavity beneath is filled with air as well as the numerous 

 surrounding intercellular cavities. These points serve the purpose of lenticels, although without their 

 typical structure. In some varieties, however, lenticels of the normal character occur. 



CORKY OR ROUGH SKIN. 

 When the epidermis is unable to keep up with the rapidly enlarging surface of the apple, it 

 may be replaced by a corky layer in patches or all over the surface, and this is broken up into 

 larger or smaller scales, which are often shed on the further growth of the fruit. Sometimes it is 

 only here and there that the epidermis is ruptured and replaced by cork, so that large patches 

 of the epidermis remain intact among the scattered corky patches. This rusty network is 

 very prominent in many pears, such as Beurre Clairgeau, and various apples, such as the 

 Reinettes. 



The corky layer originates in the epidermis itself, and only arises when the epidermis has 

 become incapable of tangential growth, in consequence of excessive thickening and cuticularization 

 of the outer wall. It is therefore generally the case that early delicate-skinned sorts remain smooth, 

 while late ripening apples and pears, whose epidermis is strongly thickened, become rough-skinned. 

 In fruits unsymmetrically developed it is always the larger side which shows a tendency to form 

 cork, because there the epidermis is exposed to such great tension that it is ruptured. 



It might appear, from this account of the formation of " russetiness," that it only occurred when 

 the conditions of growth were such that the epidermis became torn and ruptured when the fruit 

 was swelling, and these torn places were enclosed by a corky layer. But other factors must enter 

 into it, since it is a natural characteristic of many varieties. 



In some cases, at least, the amount of russetting varies according to the conditions under 

 which the apples are grown. There is a favorite shipping apple known as Dunn's Seedling or 

 Munroe's Favourite, which is so commonly russetty at the stalk end that in a description of it by 

 James Lang, of Harcourt, in the Victorian Journal of Agriculture for July, 1904, this is given as a 

 characteristic of it. "Stalk short, and set in a deep cavity, lined with russet." It might be explained 

 that the deeply-sunken stalk end showed excessively rapid growth, which caused the epidermis to 

 be ruptured and cork formed. But I find on inquiry that in Victoria and South Australia it 

 occasionally occurs perfectly smooth, more particularly when it is grown in localities which rarely 

 receive rain after the fruit is formed. North of the Dividing Range in Victoria, the cracking at 

 the stem end is only met with in wet seasons, and at other times the skin is smooth like wax, 

 even at the stalk end. In West Australia sometimes as much as 30 per cent, of the crop are free 

 from this defect. At Stanthorpe, Queensland, nearly 3,000 feet above sea-level, this variety is 

 grown in small quantities all over the district, without any scurfiness at stalk end. 



SUB-EPIDERMIS, OR HYPODERMIS. 

 The epidermis, or outer layer of the skin, is of prime importance, not only because it protects 

 the cells beneath from excessive evaporation, but because it places them in communication with 

 the oxygen of the air for respiration, and carbon dioxide for carbon-assimilation. But the inner 

 layers of cells immediately beneath the epidermis are also important, not only from contributing to 

 the firmness and thickness of the skin or rind, but from their influence on the appearance and keeping 

 quality of the fruit, owing to their green colouring matter and tannin (Fig. lOfi). Although the 

 hypodermis passes gradually into the fleshy part of the apple, yet it is distinctly different. The cells 

 composing it are smaller, tangentially elongated, or elongated parallel to the surface, with tolerably 

 thick walls, and richly provided with chlorophyll, which gives the green colour to the unripe fruit. 

 Towards the time of ripening, the green colour gradually changes to a yellow or a red, and the 

 process is similar to that which occurs in the production of the autumn tints in leaves. The red 



