VARIETIES OF RETICULATED VENATION. 159 
smaller ramifications or veinlets arise, which unite with one 
another so as to form a kind of network. Or, in the second 
modification, the fibro-vascular tissue is either continued as a 
midrib from the base to the apex of the lamina, giving off from 
its sides other veins, which run parallel to the margins, and 
which are simply connected by unbranched veinlets (jigs, 311, 
b, and 318) ; or it divides at once into several veins or ribs, which 
proceed from the base to the apex (jig. 316), or margins (fig. 
317) of the blade, more or less parallel to one another, and are 
in like manner connected only by simple parallel unbranched 
veinlets (fig. 311, a). The leaves which exhibit the first modi- 
fication of venation are called reticulated or netted-veined leaves, 
and occur universally in Dicotyledons ; and those which present 
the second modification are termed parallel-veined leaves, and 
are characteristic with some few exceptions of Monocotyledons. 
These two modifications are also subject to certain variations, 
some of which must now be noticed. 
1. Varieties of Reticulated or Netted Venation. 
There are two principal varieties of this kind of venation, 
namely, the feather-veined or pinnately-veined, and the radiated 
or palmately-veined. 
Fie. 312. Pre, 313. Fie. 314. Fic. 315. 
Fig. 312. Feather-veined leaf of the Spanish Chestnut.——Fig. 313. Feather- 
veined leaf of the Oak. Its lobes are arranged in a pinnatifid manner.—— 
Fig. 314, Leaf of the Dead-nettle. The venation is the true netted, andits 
margins are serrate. Fig. 315. a. Linear leaf, 06, Triple-ribbed leaf of 
the common Sunflower, 
A. Fetther-veined or Pinnately-veined.—In this variety the 
midrib either gives off lateral veins which proceed at once to 
