68 MANUAL OF BOTANY 



a modification of this variety, in which the ribs, instead of 

 diverging from one another, run in a curved manner from a 

 point at or near the base of the blade to the apex, towards which 

 they converge, such ribs being connected together by branching 

 veins. 



The varieties of venation correspond to the modes of branch- 

 ing of the phyllopodium already described, the fusion of the 

 wings of the branches being almost or quite complete. 



^2) Varieties of Parallel Venation. 



There are certain characteristic variations of parallel vena- 

 tion. Thus, the main veins may either proceed in a somewhat 

 parallel direction from the base to the apex of the lamina, to 

 which point they converge more or less {fig. 116), or they 

 diverge from one another towards the circumference of the 

 blade (fig. 117). The leaves of Grasses, Lilies, and the common 

 Flag may be taken as examples of the first variety ; and those 

 of many Palms {fig. 117) of the second. 



Or, the leaves may have a prominent midrib, as in the feather- 

 veined variety of reticulated venation, giving off from its sides 

 along its whole length other veins, which proceed parallel to each 

 other in a straight or curved direction towards, and lose them- 

 selves in, the margins (figs. 118 and 111, 6) ; and are connected, 

 as in the last variety, by unbranched veinlets. The Banana, the 

 Plantain, and allied plants furnish us with examples of this 

 variety. This latter variety is sometimes distinguished as the 

 curve-veined, the former being commonly known as the stradght- 

 veined or parallel-veined. 



The Shades of Leaves. 



We have seen that the freedom or coalescence of the wings 

 of the epipodium and those of its branches lead to the recogni- 

 tion of two apparently different types of leaf, the simple and 

 the oompovmd. It wiU be convenient to discuss the peculiarities 

 of these two kinds separately. 



Simple Leaves. 



The modifications which simple leaves present as regards 

 their margins, shapes, and other variations of their blades are 

 extremely numerous. They are usually considered under five 

 heads, as follows : 1. Margins ; 2. Incision ; 3. Apex ; 4. General 

 Outline ; 5. Form 



