HOW THE TISSUE OF PLANTS IS FORMED. 251 



Third. 10 parts of water and 12 parts of carbon make 

 up the composition of cellular tissue; of which the chemical 

 formula is 12 H-JO Oio. As water consists of H2 O; 10 parts 

 of it furnish the H-o Oio, which added to 12, make up the 

 cellulose (Cis H^o Oio). 



Hence when the leaves absorb carbonic acid, or receive 

 it in the sap from the roots, and the sun shines upon them, 

 the carbonic acid is decomposed and the oxygen of it is ex- 

 haled from the leaves while the carbon forms a union with 

 the elements of the water and becomes plant tissue. In 

 this combination the required mineral elements, and the 

 nitrogen of which the gluten and albumen are formed, and 

 which are derived from the sap, take their share; forming 

 the contents of the cells and the supporting framework of 

 the whole plant. 



Thus the leaves complete the work of building up the 

 fabric of the plant from the materials furnished by the soil-, 

 or by the farmer when the soil is not fully provided with 

 them. And they not only build up the plant, but they 

 store up in it the starch of which the seed mainly consists; 

 and the gluten and albumen of which the germ is formed; 

 and thus provide for a future generation to succeed them 

 after their work is done. They also, by a most mysterious 

 change, in which the very same elements are simply trans- 

 posed in some way, produce this starch from the cellulose; 

 and by the addition of more water, convert starch into the 

 sugar which makes the grape and the peach and the other 

 fruits so delicious to our palate; thus affording not only the 

 simple necessaries of animal life, but the delicacies and lux- 

 uries which make up a large part of the enjoyment of our 

 existence. 



But these functions of the leaf have a very close relation 

 to circumstances which are under the control of the farmer. 

 The vigor and luxuriance of plant growth are closely con- 

 nected with the yield of the fruit, or the seed, which is the 

 hope and aim of the cultivator of the soil. Hence how im- 

 portant it is that he should encourage this leaf growth by 

 the most perfect preparation of the soil that is possible; by per- 



