MANUAL FOR SUGAR GROWERS. 



11 



seen to consist of cells of somewhat irregular out- 

 line, while the contents are colourless; at intervals 



-e 



i* 



FIG. 4. Transverse section of sugar-cane leaf (magnified) ; a, fibro-vascular 

 bundles surrounded by (fc) layer of cells containing chlorophyll ; c, cells with 

 colourless contents and air-cells ; d, epidermis ; e, stomata. 



there will be seen pairs of cells having green con- 

 tents ; these are crescent-shaped and lie with their 

 points touching, so that there is a space between their 

 opposing faces ; this space is the opening communi- 

 cating with the interior air-spaces of the leaf ; these 

 crescent-shaped cells are known as guard-cells and 

 the whole (guard-cells and aperture) is termed a 

 stoma or mouth ; by means of these stomata the in- 

 terior cells of the leaf are in 

 intimate contact with the at- 

 mosphere. The atmosphere, 

 which for the most part is 

 composed of two gases, nitro- 

 gen and oxygen, contains also 

 a ver J sma11 quantity of a gas 

 known as carbonic acid or 

 carbon dioxide, a substance composed of carbon and 

 oxygen and having the composition represented by 



