FOEM OF LEAVES 



91 



125. Compound or branched leaf of brake 

 (which is a fern). 



191. FORM. Leaves are simple or unbranched (Fig. 

 124), and compound or branched (Fig. 125). The 

 method of compounding or branching follows the style 

 of veining. The veining, or venation, is of two general 



kinds: in most plants 

 the main veins di- 

 verge, and there is a 

 conspicuous network 

 of smaller veins : such 

 leaves are netted- 

 veined. In other 

 plants the main veins 

 are parallel, or nearly 

 so, and there is no 

 conspicuous network : 

 these are parallel- 

 veined leaves (Fig. 136). The venation of netted-veined 

 leaves is pinnate or feather-like, when the veins arise from 

 the side of a continuous midrib (Fig. 124) ; palmate or 

 digitate (hand-like), when the veins arise from the apex 

 of the midrib (Fig. 126). If the leaf were divided be- 

 tween the main veins, it would 

 be pinnately or digitately com- 

 pound. 



192. It is customary to speak 

 of a leaf as compound only when 

 the parts or branches are com- 

 pletely separate blades, as when 

 the division extends to the midrib 

 (Figs. 125, 127, 128). The parts 

 or branches are known as leaf- 

 lets. Sometimes the leaflets themselves are compound, and 

 the whole leaf is then said to be M- compound or twice- 

 compound (Fig. 125). Some leaves are three -compound, 

 four - compound, or five - compound. Decompound is a 



126. Digitate- veined peltate leaf 

 of nasturtium. 



