THE SKIN OF THE APPLE AND PEAP. 



39 



THE SKELETON. 



Just as in animal structures the skeleton is closely associated with the principal blood-vessels, 

 in order to strengthen and support them, so in the plant-body the vessels are bound up with what 

 represents a skeleton, and the whole is spoken of as a Fibro-vascular bundle. The apple starts 

 as a small fruit, and with little flesh (Fig. 74), but this gradually grows to a good size, when it 

 requires a framework to support it. Such a mass of pulpy tissue would collapse by its own weight 

 unless there were some means of strengthening it. The distended cell-walls of the tissue itself 

 would tend to stiffen it, just as in a firm leaf, when the cells are all turgid ; but strengthening rods 

 are required as well. There are ten of these curved supports, like the ribs of an umbrella, 

 normally equidistant from each other, diverging from the stalk at the base, and uniting again at 

 the top, just beneath the eye. These strengthen the whole structure, like so many curved ribs, 

 and the various branches form lesser supports. It will be observed that this system of strengthening 

 is not merely mechanical ; it is also a living mechanism, which has to grow and expand according 

 to the strain it has to bear. The young fruit of a Cleopatra apple, when the petals have just fallen, 

 and fertilization has occurred, is about one-eighth of an inch in diameter, and forms a direct 

 continuation of the stalk, being completely enveloped by a dense mass of silky hairs, which are 

 readily scraped off. When placed in a dilute solution of caustic potash it becomes of a dark, 

 ruddy-brown colour, and is thereby sharply marked off from the green stalk. The bulk of the 

 young fruit consists of the " core," as seen in section (Fig. 74), which has the ten primary vascular 

 bundles surrounding its margin, and there is a thin layer of parenchymatous tissue between them 

 and the skin. After macerating for four or five days in the caustic potash, the skin can easily be 

 removed, and just immediately beneath it there is the fine network of vessels, just as in the mature 

 apple, only of exceeding fineness, like a spider's web (Fig. 93). So this wonderful network of 

 vessels exists from the earliest stages of the fruit, and has to go on growing and expanding until 

 maturity is reached, always accommodating itself to and endeavouring to keep pace with the 

 enlarging bulk of the flesh. 



The skin is likewise a form of skeleton, giving firmness and consistency to the entire fruit, 

 but its structure and functions will be considered in the next section. 



XIV. — THE SKIN OF THE APPLE AND PEAK. 



The skin is not only a form of skeleton, but it has an important influence on the amount of 

 moisture given off from the fruit, and its main function is to regulate transpiration. It is noticeable 

 how quickly an apple or pear will dry up or decay when it is pared. As showing the efficiency of the 

 skin for the purpose, I had a pear of the Broompark variety and a Jonathan apple peeled and 

 unpeeled, and kept in a dry atmosphere for 48 hours. The loss in weight was carefully tested by 

 Mr. !\ R. Scott, Chemist for Agriculture, with the following results : — 



Table VI. -Loss of Water in Whole and Peeled Apples and Peaks after 48 Hours. 



Weight of whole pear before desiccation, 261.569 gr. ; after, 260.0355 gr. 

 Weight of peeled pear before desiccation, 176.677 gr. ; after, 172.5190 gr. 

 Weight of whole apple before desiccation, 133.4895 gr. ; after, 132.737 gr. 

 Weight of peeled apple before desiccation, 112.065 gr. ; after, 108.8538 gr. 

 No. 1 whole pear, 0.586 per cent, loss after 48 hours. 

 No. 2 peeled pear, 2.35 per cent, loss after 48 hours. 

 No. 3 whole apple, 0.563 per cent, loss after 48 hours. 

 No. 4 peeled apple, 2.87 per cent, loss after 48 hours. 



