OUTLINES OF BO t ANY. V 



37. Zieavea are 



sessile, when the blade rests on the stem without the intervention of a petiole. 



amplexicaul or stejii- clasping, when the sessile base of the blade clasps the stem horizontally. 



perfoliate, when the base of the blade not only clasps the stem, but closes round it on the 

 opposite side, so that the stem appears to pierce through the blade. 



decurrent, when the edges of the leaf are continued down the stem so as to form raised lines 

 or narrow appendages, called loings. 



sheathing, when the base of the blade, or of the more or less expanded petiole, forms a 

 vertical sheath round the stem for some distance above the node. 



38. Leaves and flowers are called radical, when inserted on a rhizome or stock, or so close to 

 the base of the stem as to appear to proceed from the root, rhizome, or stock ; cauline, when 

 inserted on a distinct stem. Eadical leaves are rosulate when they spread in a circle on the 

 ground. 



39. Reaves are 



simple and entire, when the blade consists of a single piece, with the margin nowhere 

 indented, simple being used in opposition to ccmipound, entire in opposition to dentate, lobed, or 

 divided. 



ciliate, when bordered with thick hairs or fine hair-like teeth. 



dentate or toothed, when the margin is only cut a little way in, into what have been 

 compared to teeth. Such leaves are serrate, when the teeth are regular and pointed like the teeth 

 of a saw ; crenate, when regular and blunt or rounded (compared to the battlements of a tower) ; 

 serrulate and crenulate, when the serratures or orenatures are small ; sinuate, when the teeth are 

 broad, not deep, and irregular (compared to bays of the coast) ; wavy or undulate, when the edges 

 are not flat, but bent up and down (compared to the waves of the sea). 



lobed or cleft, when more deeply indented or divided, but so that the incisions do not reach 

 the midrib or petiole. The portions thus divided take the name of lobes. When the lobes are 

 narrow and very irregular, the leaves are said to be laciniate. The spaces between the teeth or 

 lobes are called sinuses. 



divided or dissected, when the incisions reach the midrib or petiole, but the parts so divided 

 off, called segments, do not separate from the petiole, even when the leaf falls, without tearing. 



compound, when divided to the midrib or petiole, and the parts so 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 common stalk upon which the leaflets are inserted is called the common 

 petiole or the rhachis ; the separate stalk of each leaflet is a petiolule, 



40. Leaves are more or less marked by veim-s, 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-vdned. 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 mathe- 

 matically so. When 3 or 5 or more ribs or nerves diverge from the base, the leaf is said 

 to be 3-nerved, 5-nerved, etc., but if the lateral ones diverge from the midrib a little aibove the 

 base, the leaf is triplinerved, quintuplinerved, etc. The arrangement of the veins of a leaf is 

 called their venation 



41. The Xieaflets, Segrments, Ziobes, or 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 the terminal lobe or segment is much larger and broader than the lateral ones, 

 compared, by a stretch of imagination, to a lyre ; nmcinate, when the lateral lobes are curved 

 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, compared 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 pinvMte, 

 palmate, pedate, eta., leaves. If they are so cut into segments only, they are usually said to be 

 pirmatisect, palmatisect, pedatisect, etc., although the distinction beween 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, palmatifid, pedatifid, etc. 



