52 THE INTERNAL 



curious, is, that these cells, which have all been formed in 

 the same way, and even when their subsequent shape remains 

 exactly the same, have the power of producing the most 

 varied substances in their interior, and thus become a 

 means, in the hand of Nature, of multiplying to infinity the 

 riches and beauty of the vegetable world. 



This leads us to the peculiar vital processes of the 

 vegetable cell. Every separate cell has, as it were, its own 

 especial life. Its walls, indeed, are not perforated, but, 

 nevertheless, the fluid which it requires for its nutrition 

 makes its way in. This is composed of water, carbonic 

 acid, salts of ammonia and other soluble salts of the soil. 

 The few substances absorbed by the cell, become changed 

 by its peculiar power, and from them are formed all 

 the various materials which give the plant value, either 

 in the eyes of the aesthetic observer, or in the household of 

 the economist. 



A great many cells contain merely colourless sap, this is 

 the case with the wood and bass-cells ; many merely air, 

 as for instance, the so-called vessels. But others display 

 the most splendid tints in their juices, some giving flowers 

 and fruits the charm of their lovely enamelling of colour, 

 while others cause various parts of plants, otherwise green, 

 to assume a chequered, mottled aspect (PL n, Fig. 7.) 

 Here we find every shade of red, blue and yellow. The 

 green colouring of plants depends, on the other hand, 

 on wholly different causes, for the sap of plants is never 

 green. When we examine, with the microscope, cells 

 which to the naked eye seem green, we see that the green 

 appearance is produced by separate granules of a green 

 substance (chlorophylle, or leaf-green,) which adhere to 

 the inside of the wall of the cell (PI. i, Fig. 2, 13, c.) The 

 splendid colour, indigo, is nothing but a peculiar modification 



