SECTION 7.] 



ORDINARY LEAVES. 



51 



veined, — terms which it is convenient to use, although these " nerres " 

 and " veins " are all the same thing, and have no likeness to the nerves and 

 little to the veins of animals. 



129. Netted-veined leaves belong to plants which have a pair of seed- 

 leaves or cotyledons, such as the Maple (Fig, 20, 24,), Beech (Fig. 33), and 



the like ; while parallel-veined or nerved leaves belong to plants with one 

 cotyledon or true seed-leaf; such as the Iris (Fig. 59), and Indian Corn 

 (Fig. 70). So that a mere glance at the leaves generally tells what the 

 structure of the embryo is, and refers the plant to one or the other of these 

 two grand classes, — which is a great convenience. For when plants diifer 

 from each other in some one important respect, they usually differ corres- 

 pondingly in other respects also. 



130. Parallel- veined leaves are of two sorts, — one kind, and the com- 

 monest, 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 common Pickerel-weed of our 

 ponds, in the Banana, in Calla (Fig. 114), and many similar plants of 

 warm climates. 



131. Netted-veined leaves are also of two sorts, as in the examples al- 

 ready referred to. In one case the veins all rise from a single rib (the 

 midrib), as in Fig. 112, 116-127. Such leaves are called Feather-veined 

 or Penni-veined, i. e. Pinnaiefy-veined ; both terms meaning the same thing, 

 namely, that the veins are arranged on the sides of the rib like the plume 

 of a feather on each side of the shaft. 



Fio. 113. A (paTallel-veined) leaf of the Lily of the Valley. 111. One of the 

 Calla Lily. 



