OUTLINES OF BOTANY. XVll 



34. A culm is a name sometimes given to the stem of Grasses, Sedges, 

 and some other Monocotyledon ous plants. 



§ 5. The Leaves. 



35. The ordinary or perfect Xieaf consists of a flat blade or lamina, 

 usually green, and more or less horizontal, attached to the stem by a stalk 

 called a, footstalk or 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. 



36. The end by which a leaf, a part of the flower, a seed, or any other 

 organ, is attached to the stem or other organ, is called its base, the op- 

 posite end is its apex or summit, excepting sometimes in the case of anther- 

 cells (115). 



37- leaves are 



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

 a petiole. 



amplexicaul or stem-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 wings. 



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. 

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



39. 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 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 crenatures 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 (com- 

 pared 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 



