LEAF-SURFACE 153 



When the leaves are broader, as in the MELAS- 

 TOMACE^E, and ARACE^E, the veins curve outwards 

 like bows and come together again at the tip. This 

 is really of the same parallel type, adapted to the 

 greater breadth of the leaf, but to distinguish it from 

 the truly parallel type is termed basal. 



Pinnate venation. In most leaves there is one 

 central vein termed the mid-rib which bears side veins 

 to right and left, these side veins again branching 

 in all directions. This is termed pinnate or feather 

 veining. In some leaves, e.g. in the common Plantain 

 (MUSA), the side veins run straight from the mid-rib 

 to the edge of the leaf, and are connected together 

 by very much smaller cross veins. This is the most 

 typical form of pinnate venation being very like a 

 feather, and is easily torn by a slight wind. In some 

 leaves the side veins are fewer and comparatively 

 strong and run straight to the margin where they 

 end in teeth, but in most cases they curve for- 

 wards towards the margin of the leaf and join 

 each other in a more or less regular marginal vein, 

 as in Ficus RELIGIOSA (the Peepul, fig. 33), and 

 PLUMERIA (figs. 26 and 27). The side veins are 

 joined by secondary veins and these branch again, 

 forming a net-work of veins, described often as 

 reticulate venation, as distinguished from the parallel 

 cross venation of grasses and the parallel secondary 

 venation of the Plantain leaf. 



Palmate venation. In some leaves, e.g. in Cotton, 

 STERCULIA, ZIZYPHUS, three, five or more veins start 

 from the petiole and radiate like the bones in the 

 palm of a hand straight through the blade, ending 



