21 



with the naked eye run approximately parallel to one another 

 They usually run from the base of the leaf to the apex, as in a 

 Grass, or Bamboo. The term, however, is also applied to cases 

 where there is one main strand traversing the leaf-blade from 

 base to apex, called the midrib, and from which all other 

 noticeable strands run approximately parallel to each other 

 towards the leaf-margin, as in a Banana leaf. In both cases a 

 few minute, inconspicuous, and generally straight, strands 

 usually connect the main strands and run at right angles to 

 them. These are conspicuous in the leaves of Arundinaria 

 spathiflora. In reticulate venation the strands are seen to 

 branch in all directions and thus give rise to an elaborate net- 

 work, as in a Teak leaf. When there is a distinct midrib from 

 which all the other nerves, directly or indirectly, spring, the 

 nerves which spring from the midrib are called lateral nerves 

 and the leaf is said to be penninerved, or pinnately-veined. In 

 such cases also the midrib is said to be the primary nerve, the 

 larger nerves springing from the midrib are called secondary 

 nerves, and the smaller nerves springing from the latter the 

 tertiary nerves. 



In some cases in this type of leaf, the lower pair or two of 

 lateral nerves are much more prominent than the remainder, 

 as in Cinnamomum Camphora, see Fig. 5, Plate IV. Such 

 cases bring us by insensible gradations to the next type of 

 venation in which there is more than one main rib, or primary 

 nerve, entering the base of the blade and the leaf is then said 

 to be palminerved, or palmately- or digitately -veined. Accord- 

 ing to the number of the strong basal nerves the leaf is said to 

 be palmately or digitately 5 nerved, 7 nerved and so on. 



Nerves may be straight or more or less curved. Those 

 which are slightly bent in the form of a bow and run in a 

 regular sweeping curve are called arcuate, those which are 

 more sharply bent are arched. A leaf of Quercus incana may 

 be taken as an example of a penninerved leaf with straight- 

 secondary nerves, see Fig. 1, Plate IV. Such a leai differs 

 from a typical parallel-veined leaf, such as that of the Banana, 

 in having the secondary veins further apart and the spaces 

 between them rilled with distinctly reticulated strands. A 

 leaf of Acer caesium, Fig. 2, Plate IV, furnishes an example 

 of a palminerved leaf with straight primary nerves. The 

 penninerved leaf of Cornus macropliylla, Fig. 3, Plate IV, 

 has arcuate secondary nerves. The palminerved leaf of 

 Smilax parvifrtia, Fig. 4, Plate IV. has arcuate primary nerves. 

 By some botanists the term palminerved is restricted to cases 



