KINDS 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 Wetted-verned or Reticulated, and, 2d, 
the Parallel-veined or Nerved. 
126. Netted-Yeined 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 veinlets 
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- eu ainehedTawwearat 
bryo (48), and stems 8 Linden. 84, Maple. 
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), é&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 (118). 
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