10 GARDEN FARMING 



function is, of course, the most important one and consists in 

 gathering from the soil the crude mineral foods which are used by 

 the plant. These foods are usually about twelve in number, the 

 most important of which are nitrogen, potash, phosphoric acid, lime, 

 magnesia, silica, iron, and sulphur. These materials are gathered 

 from the soil in solution that is, carried in water by the 

 growing tissue of the roots. This growing tissue is usually situ- 

 ated in a comparatively restricted region near and at the tip of 

 the root. This actively growing tissue is called by botanists 

 meristem tissue, and so long as the cells in the neighborhood 

 of the tip of the root remain in an actively dividing condition 

 they belong to the class of meristem tissue ; but as soon as they 

 lose this function and become fixed in form their outer surface 

 changes in character and becomes thicker and less able to take up 

 mineral matters from the soil. Young actively growing roots are 

 therefore essential to the rapid development of crops ; and since 

 the rapid development of vegetables is a very desirable feature, the 

 soil conditions should be such as to induce rapid growth. After 

 the crude materials which form the foods of plants are taken up 

 from the soil they are carried through the older tissue, which is 

 provided with ducts and channels through the stem to the leaves. 



Stem. The stem acts as a framework to support the leaves, 

 flowers, and ultimately the fruit, and as a means of conducting to 

 the leaves the food which is gathered by the root. In fact, the stem 

 has one system of pipes or ducts through which the crude material 

 is carried to the leaves and another system through which the fin- 

 ished products ready for use in plant growth are carried back to 

 the various parts of the stem and to the root, where they are either 

 stored up or used in building additional tissue in stem or root. 

 The function of the stem, therefore, is largely mechanical rather 

 than physiological. 



Leaf. The leaves are the most exposed of the delicate organs 

 of the plant, and their functions are more complex than those of 

 any other plant organ. Leaves are usually broad, thin, and so 

 arranged as to have a very large area exposed to the air and sun. 

 Under normal conditions they are usually green in color. There 

 are a few exceptions to this, as in the case of beets and some other 

 plants with colored leaves. Both the broad expanse of leaf surface 



