CHAPTER XXVII. 



THE ANTHOPHYTA, LEAVES, REPRODUCTIVE ORGANS AND 



FRUIT. 



THE anthophyta, or flowering plants, make up the greater 

 part of the vegetable kingdom. They include the common herbs, 

 shrubs and trees, the plants that are cultivated for pleasure and 

 profit, the plants that furnish materials for the food, clothing 

 and shelter of man. 



Among these plants, the stem, roots and leaves are usually well 

 developed and the three tissue systems are clearly defined. And 

 there is a strict division of labor in all physiological functions, 

 indicating a more complex and highly developed organism than 

 among the plants already studied. 



Leaves are organs of assimilation, and in a modified form 

 constitute the organs of reproduction for this group of plants, 

 so that they seem the most important parts of the plant. A 

 leaf consists of a vascular framework covered by a mass of par- 

 enchyma, whose cells are well supplied with chlorophyll, and the 

 whole covered with a delicate epidermis. The parts of a leaf are 

 the stalk or petiole, and the blade or expanded portion, and at 

 the base of the petiole there are sometimes leaf-like bodies called 

 stipules. The petiole continued through the leaf is the midrib, 

 and its branches and subdivisions are called ribs, veins and vein- 

 lets. The framework of the leaf is a branch from the vascular 

 system of the stem. 



On the basis of the arrangement of the veins, leaves are 

 divided into two classes, namely netted- veined, as the leaves of 

 the apple and oak, the veins forming a conspicuous net work, and 

 the parallel- veined, as the leaves of corn and grass, in which 

 there are few branches, and no net work is formed. 



Leaves vary greatly in form, some of the more common forms 



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