138 



AGRICULTURAL BOTANY 



Apex 



Get a number of twigs and examine the leaf arrange- 

 ment. 



Parts of the Leaf. - - The main part of the leaf is called 

 the blade. The blade is attached to the stem or branch 

 by a petiole. At the base of the 

 petiole, and sometimes clasping the 

 stem, are often found leaflike or 

 thorny appendages, called stipules. 

 The part of the blade farthest re- 

 moved from the petiole is called 

 the apex. The part of the blade 

 nearest the petiole is called the 

 base of the leaf. The framework 

 of the blade is made up of fibrous 

 material, called ribs and veins. 

 From the base of the leaf, running 

 through the blade to the apex, is 

 the largest of the ribs, called the 

 midrib. The branches are called 

 veins, and the smaller ones veinlets. 

 Venation of Leaves. Vena- 

 ' tion is the plan of distribution of 

 ribs and veins to the leaf blade. Leaves are either 

 netted-veined or parallel-veined. 



Netted-veined leaves, as the name indicates, have 

 veins branching from the midrib, dividing and sub- 

 dividing until the whole leaf blade is covered with 

 a fine network. This venation is clearly shown in 

 the leaf of the beet, the oak, and the maple. In gen- 

 eral the exogenous plants are netted-veined. 



Parallel-veined leaves have small parallel ribs run- 

 ning from the base of the midrib throughout the blade, 

 but without branching, although there are minute 



Petiole- 

 Stipule 



Stipule 



