INTROBrCTIOK. 7 



80 divided off, called segments, do not separate from the petiole, even when 

 the leaf falls, without tearing. 



compo'jnd, when divided to the midrib or petiole, and the parts so di- 

 vided 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. 



Leaves are more or less marked by veins, wliich, starting from the stalk, 

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

 visibly. These veins contain the vessels by which the sap is carried from 

 the stem and petiole to the surface of the leaf. The principal ones, when 

 prominent, are often called ribs or nerves, the smaller branches only then 

 retaining the name of veins. 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 sUghtly without branching, and converge again 

 towards the summit, they are said to be parallel, although not mathemati- 

 cally so. 



The veins of leaves, as also their lobes, segments, or leaflets, are 



pinnate, when there are several succeeding each other on each side of the 

 midrib or petiole, compared to the branches of a feather. A leaf with jjin- 

 nate lobes is sliortly called pinnatifid. A pinnately-lobed or divided leaf is 

 called lyrate when the terminal lobe or segment is much larger and broader 

 than the lateral ones, comjiared, by a stretch of imagination, to a lyre ; rnn- 

 cinate, when the lateral lobes are ciuwed backwards towards the stem. 



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

 pared to the fingers of the hand. A leaf with palmate lobes is shortly 

 called palmatifid. 



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 vrith allied plants. A leaf with ternate lobes 

 is called trifid. A leaf with tlu-ee leaflets .is sometimes improperly called a 

 ternate leaf: it is the leaflets that arc ternate. Ternate leaves are leaves 

 growing three together. 



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

 are forked, the outer one 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. A leaf with pedate lobes is called pedatifid. 



The teeth, lobes, segments, or leaflets, may be agaia toothed, lobed, di- 

 vided, or compounded. Some leaves are even three or more tunes divided 

 or compounded. 



The number of leaves or their parts is expressed adjectively by the follow- 

 ing numerals, derived from the Latin : — 



uni-, bi-, tri-, quadri-, quinque-, sex-, septem-, octo-, novem-, decern-, etc., mnlti- 

 1-, 2-, 3-, 4-, 5-, 6-, 7-, 8-, 9-, 10-, many- 



prefixed to a termination, indicating the particular kind of part referred to. 

 Thus— 



unidentate, bidentate, multidentate, mean one-toothed, two-toothed, 

 many-toothed, etc. 



bifid, trifid, multifid, mean two-lobed, three-lobed, many-lobed, etc. 



unijoliolate, bifoliolate, multifoliolate, mean with one leaflet, with two 

 leaflets, with many leaflets, etc. 



unifoliate, bifoliate, mwltifoliate, mean with one leaf, with two leaves, 

 •with many leaves, etc. 



Leaves or their parts, or any other flat organs m plants, are 



linear, when long aud narrow, at least foui* or five times as long as broad. 



