Leaves and their Work 167 



these are all carbon compounds ; so that altogether 

 the pound of flour contains some seven ounces of 

 carbon. 



Some of the palms, as the sago palm, use very large 

 quantities of carbon in forming the starch of their 

 pith : one tree, for instance, often yielding the extra- 

 ordinary amount of 800 lbs. of starch. All the sugars, 

 oils, gums, caoutchoucs, of the vegetable world, contain 

 large quantities of carbon, and so also do the fibres 

 of cotton, flax, hemp and others. 



But, as already said, carbon forms part ' of the 



Surface leaf-cells, with pores, magnified. 



structure of every portion of a plant from root to seed, 

 and it enters largely into the composition of the 

 skeleton, or frame-work, both of stems and leaves ; for 

 a plant's skeleton consists of fibre, identical in com- 

 position with the fibres of the cotton and other plants 

 used for weaving purposes. 



Now, both the skeleton and the flesh of a plant, 

 every part of it, indeed — roots, stems, leaves, flowers, 

 fruit, seed — consists either of a single cell, or of an 

 assemblage of cells, which may be compared with the 



