MODES OF VEINING 



89 



105. Veining. The blade of the leaf is traversed by a frame- 

 work of fibro-vascular bundles known as veins. These are 

 arranged in many ways, but the two prin- 

 cipal types are closed, or parallel-veined, 



and open, or netted-veined, leaves. In the 

 former the veins run more or less nearly 

 parallel, either from base to tip of the 

 leaf, or from a mid- 

 rib outward. In the 

 latter the veins are 

 branched so as to 

 form a network. 



106. Palmate and 

 pinnate veining. In 

 netted-veined leaves 

 several ribs may 

 radiate from the end 

 of the petiole, like 

 the sticks of a fan. 

 Such veining is said 

 to be palmate. If 



there is only one midrib, from which smaller ribs extend both 

 ways, the veining is said to be pinnate (meaning feather-like). 



Often the veining is intermediate be- 

 tween these two types. 



107. Relation of shape to mode of 

 veining. Since the water supply of 

 the leaf is carried through the veins, 

 and since they support the softer 

 parts between them, one would ex- 

 pect to find that the form of the leaf 

 would bear a close relation to its 

 mode of veining. This is the case, 

 and hi general palmately veined 

 leaves are roundish, while pinnately 



FIG. 91. Parallel-veined 

 leaf of Solomon's seal 



After Strasburger 



FIG. 92. Parallel vein- 

 ing in canna. Veins 

 running from midrib 

 to margin 



FIG. 93. Netted veining (pal- 

 mate) in leaf of melon 

 After Decaisne 



