SECTION 



7-3 



ORDINARY LEAVES. 



51 



veined, — terms vrhich it is convenient to use, although these "nerves" 

 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 (Pig. 20, 24,), Beech (Pig. 33), and 



tie 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 

 (Pig. 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. Por when plants differ 

 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 (Pig. 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 Pig. 112, 116-127. Such leaves are called Feather-veined 

 or Penni-veined, i. e. Pinnately-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. 



Fig. 113. A (parallel-veined) leaf of the Lily of the Valley. 

 Calla Lily. 



114. One of the 



