XVlll OUTLINES OF BOTAOT. 



divided off, called leaflets, separate, at least at the fall of the leaf, from the 

 petiole, as the whole leaf does from the stem, without tearing. The com- 

 mon stalk upon which the leaflets are inserted is called the common petiole 

 or the rachis ; the separate stalk of each leaflet is a petiolule. 



40. Leaves are more or less marked by veins, which, starting from the 

 stalk, diverge or branch as the blade widens, and spread all over it more or 

 less visibly. The principal ones, when prominent, are often called ribs or 

 nerves, the smaller branches only then retaining the name of veins, or the 

 latter are termed veinlets, The smaller veins are often connected together 

 like the meshes of a net, they are then said to anastomose, and the leaf is 

 said to be reticulate or net- veined. When one principal vein runs direct 

 from the stalk towards the summit of the leaf, it is called the midrib. 

 When several start from the stalk, diverge slightly without branching, and 

 converge again towards the summit, they are said to be parallel, although 

 not mathematically so. When 3 or 5 or more ribs or nerves diverge from 

 the base, the leaf is said to be S-nerved, o-nerved, etc., but if the lateral 

 ones diverge from the midrib a little above the base, the leaf is triplinerved, 

 quintuplinerved, etc. The arrangement of the veins of a leaf is called their 

 venation. 



41. The leaflets. Segments, Lobes, Veins of leaves are 

 pinnate (feathered), when there are several succeeding each other on 



each side of the midrib or petiole, compared to the branches of a feather. 

 A pinnately lobed or divided leaf is called lyrate when the terminal lobe 

 or segment is much larger and broader than the lateral ones, compared, by 

 a stretch of imagination, to a lyre ; runcinate, when the lateral lobes are 

 surved backwards towards the base of the leaf ; pectinate, when the lateral 

 lobes are numerous, narrow, and regular, like the teeth of a comb. 



palmate or digitate, when several diverge from the same point, com- 

 pared to the fingers of the hand. 



ternate, when three only start from the same point, in which case the 

 distinction between the palmate and pinnate arrangement often ceases, or 

 can only be determined by analogy with allied plants. A leaf with ternate 

 lobes is called trifid. A leaf with three leaflets is sometimes improperly 

 called a ternate leaf; it is the leaflets that are ternate ; the whole leaf is 

 trifoliolate. Ternate leaves are leaves growing three together. 



pedate, when the division is at first ternate, but the two outer branches 

 are forked, the outer ones of each fork again forked, and so on, and all the 

 branches are near together at the base, compared vaguely to the foot of a 

 bird. 



42. Leaves with pinnate, palmate, pedate, etc., leaflets, are usually for 

 shortness called pinnate, palmate, pedate, etc., leaves. If they are so cut 

 into segments only, they are usually said to be pinnatisect, palmatisect, 

 pedatisect, etc., although the distinction between segments and leaflets is 

 often unheeded in descriptions, and cannot indeed always be ascertained. If 

 the leaves are so cut only into lobes, they are said to be pinnatifid, pal- 

 matifid, pedatijid, etc. 



43. The teeth, lobes, segments, or leaflets, may be again toothed, lobed, 

 divided, or compounded. Some leaves are even three or more times divided 

 or compounded. In the latter case they are termed decompound. When 

 twice or thrice pinnate (bipinnate or tripinnate), each primary or secondary 

 division, with the leaflets it comprises, is called & pinna. When the pinnae 

 of a leaf or the leaflets of a pinna are in pairs, without an odd terminal 



