6 INTBODUCTION. 



Branches are 



forked, when, instead of proceedmg from the side of a main stem, the 

 stem itself is divided into two equal branches. 



dichotomoiis, when each fork is again forked, or the same mode of divi- 

 sion is several times repeated. 



trichotomous, when divided in the same manner into three branches at 

 each division instead of two. When the middle branch is evidently the 

 principal one, the stem is usually said to have two opposite branches ; if 

 the central one is smaller or not larger than the two others, the word tri- 

 chotomous is applied. 



umbellate, when divided in the same manner into several branches, 

 with the central one not larger than the others. 



§ 5. The Leaves. 



The ordinary perfect Leaf consists of a fiat blade or lamina, usually 

 green, and more or less horizontal, supported on, or connected with the stem 

 by a stalk called a petiole. 



When the form or dimensions of a leaf are spoken of, it is generally the 

 blade that is meant, without the petiole or stalk. 

 Leaves are 



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

 petiole. 



amplexicatd, or stem-clasping, when the sessile base of the blade is not 

 a mere point, but forms more or less of a ring, clasping the stem horizon- 

 tally. 



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 leaf itself. 



decurrent, when the edges of the leaf are continued dovra 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. 



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. 



Radical leaves are rosulate, when they spread in a circle on the ground. 

 Leaves are 



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

 margin nowhere indented, simple being used in opposition to compound, 

 entire in opposition to dentate, lobed, or divided. 



ciliate, when bordered vsdth thick hairs, or fine hair-Uke 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) ; sinuate, when broad, 

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

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



lohed, or cleft, when more deeply indented or divided, but so that the 

 incisions do not reach the midrib or petiole. The teeth of these leaves take 

 the name of lobes. 



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



