5G 



MORPHOLOGY OF LEAVES AS FOLIAGE. [LESSON 8. 



veinlets, and the branches unite with each other to form meshes of 

 network. That is, they anastomose, as anatomists say of the veins 

 and arteries of the body. The Quince-leaf, in Fig. 83, shows this 

 kind of veining in a leaf with a single rib. The Maple, Basswood, 

 and Buttonwood (Fig. 50) show it in leaves of several ribs. 



141. In parallel-veined leaves, the whole framework consists of 

 slender ribs or veins, which run parallel with each other, or nearly 

 so, from the base to the point of the leaf, not dividing and sub- 

 dividing, nor forming meshes, except by very minute cross-veinlets. 

 The leaf of any grass, or that of the Lily of the Valley (Fig. 84) 

 will furnish a good illustration. 



142. Such simple, parallel veins Linnaeus, to distinguish them, 



called nerves, and parallel-veined leaves 

 are still commonly called nerved leaves ; 

 while those of the other kind are said to 

 be veined; terms which it is conven- 

 ient to use, although these " nerves " and 

 " veins " are all the same thing, and have 

 no likeness to the nerves of animals. 



143. Netted-veined leaves belong to 

 plants which have a pair of seed-leaves 

 or cotyledons, such as the Maple (Fig. 1 

 -7), Beech (Fig. 15), Pea and Bean 

 (Fig. 18, 20), and most of the illustra- 

 tions in the first and second Lessons. 

 While parallel-veined or nerved leaves 

 belong to plants with one cotyledon or 

 true seed-leaf; such as the Iris (Fig. 134) 

 and Indian Corn (Fig. 42). So that a mere glance at the leaves 

 of the tree or herb enables one to tell what the structure of the 

 embryo is, and to refer the plant to one or the other of these two 

 grand classes, which is a great convenience. For generally when 

 plants differ from each other in some one important respect, they 

 differ correspondingly in other respects as well. 



144. Parallel-veined leaves are of two sorts ; one kind, and the 

 commonest, having the ribs or nerves all running from the base to 

 the point of the leaf, as in the examples already given ; while in 

 another kind they run from a midrib to the margin ; as in the com- 



FIG. 84. A (parallel-veined) leaf of the Lily of the Valley. 



