KINPS AND FORMS OF LEAVES. 



45 



Nor are what we call veins to be likened particularly to the bloodvessels of ani- 

 mals. But this name is not so bad ; for the minute fibres which, united in bun- 

 dles, make up the ribs and veins, are hollow tubes, and serve more or less for con- 

 veying the sap. 



125. As to the veining, or the arrangement of the framework in the blade, leaves 

 are divided into two classes, viz. . 1st, the Netted-veined or Seticidated, and, 2d, 

 the Parallel-veined or Nerved. 



126. Nctted-Vcined or Reticulated leaves are those in which the veins branch off 

 from the rib or ribs, and divide again and again, and some of the veins and veiulets 

 run into one another, 



so forming reticulations 

 or meshes of network 

 throughout the leaf. 

 This is shown in the 

 Quince-leaf (Fig. 82) ; 

 also in the Linden or 

 Basswood (Fig. 83), 

 and the Maple (Fig. 

 84), where the finer 

 meshes appear in one 

 or two of the leaves. 



127. Netted-veined 

 leaves belong to plants 

 which have a pair of 

 seed-leaves to their em- 

 bryo (48), and stems 

 of the exogenous structure (115). That is, these three kinds of structure, in em- 

 bryo, stem, and leaf, generally go together. 



128. Parallel-veined or Nerved leaves are those in which the ribs and veins run side 

 by side without branching (or with minute cross-veinlets, if any) from the base to 

 the point of the blade, as in Indian-Corn, Lily of the Valley (Fig. 85), &c., or 

 sometimes from the midrib to the margins, as in the Banana and Calla (Fig. 86). 

 Such parallel veins have been called Nerves, as just explained (124). Leaves of this 

 sort belong to plants with one cotyledon to their embryo (47), and with endogenous 

 stems (113). 



Netled-veiiied Leaves ol 



84. MaiJle. 



