XVill OUTLINES OF BOTANY. 
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.!: Thecom- 
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 itmore or 
less visibly. The principal ones, when prominent, are often callediriés or 
nerves, the smaller branches only then retaining the name of veims, 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 léaf is 
said to be retzculate 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 38-nerved, 5-nerved, etc., but if the lateral 
ones diverge from the midrib a little above the base; the leaf is triplinerved, 
guintuplinerved, 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'comh, | 
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 ¢rifid. 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, ete., leaves. If they are so cut 
into segments only, they are usually said to be pinnatisect, palmatisect, 
pedatisect, ete., 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, pedatifid, ete. xX 
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 a pinna. When the pinnee 
of a leaf or the leaflets of a pinna are in pairs, without an odd terminal 
