FORM AND STRUCTURE 



The roots of the deciduous trees of North America are 

 usually a modified form of the tap root, often a divided tap 

 root with fibrous rootlets. 



STEM. 



The stem is that part of the plant axis which bears the 

 leaves, flowers and fruit, and is the means of communication 

 between them and the root. The stem differs from the root 

 not only in that it is leaf-bearing but its branches are ar- 

 ranged regularly and the growing point is at the apex of the 

 branches. A stem increases in length by the growth of a 

 terminal bud and its branches normally originate from buds. 



The points on the stem where the leaves appear are called 

 nodes. 



The parts of the stem between the nodes are called inter- 

 nodes. 



The angle formed by the upper side of a leaf and the stem 

 is called the axil. 



LEAVES. 



Leaves are stem-appendages and consist of expansions of 

 the stem tissues. Foliage leaves are usually flat, bi-laterally 

 symmetrical organs, green in color, and 

 presenting a distinct upper and under 

 surface. They are pre-eminently the 

 assimilating organs of the plant ; out 

 of the crude sap under the influence of 

 light and air they elaborate the plant 

 food. 



A Typical Leaf consists of three 

 parts, the blade, the petiole, and the 

 stipules ; any one of these parts may 

 be wanting. (Fig. 3.) 



The Blade is the expanded portion of 

 the leaf and the part to which the word 

 leaf is usually applied. The Petiole is 

 the leaf stalk. The Stipules are small 

 leaf-like bodies, borne at the base of the petiole, usually 

 one on each side. These are often united. Frequently 



504 



Fig. 3. — A Typical Leaf. 



