74 



teger), as in figs. 149 and 150; if there are slight projections of cellular 

 or vascular tissue beyond the margin, the leaf is not entire (fig. 136); 

 when the projections are irregular and more or less pom ted, the leaf 

 is dentate or toothed (fig. 155); when they lie regularly over each 

 other, like the teeth of a saw, the leaf is serrate (figs. 136, 154); when 

 they are rounded, the leaf is crenate (fig. 159). If the divisions extend 

 more deeply than the margin, the leaf receives different names accord- 

 ing to the nature of the segments: thus, when the divisions extend 

 about halfway down (figs. 134, 144), it is cleft (Jissus), and its segments 



139 



140 



141 



are called fissures (fissura, a cleft); when the divisions extend nearly 

 to the base or to the midrib (fig. 170), the leaf is partite, and its 

 segments are called partitions. 



147. These divisions take place in simple leaves exhibiting differ- 

 ent kinds of venation, and thus give rise to marked forms. Thus, if 

 they occur hi a feather-veined leaf (fig. 137), it becomes either pin- 

 natifid (pinna, a wing or leaflet, and Jissus, cleft), when the segments 

 extend to about the middle and are broad; or pectinate (pecten, a 

 comb), when they are narrow; or pinnatipartite, when the divisions ex- 

 tend nearly to the midrib. These primary divisions may be again sub- 

 divided in a similar manner, and thus a feather-veined leaf will become 

 lipinnatifid (fig. 138), or bipinnatipartite ; and still further subdivisions 

 give origin to tripinnatifid and laciniated leaves. If the divisions of a 

 pinnatifid leaf are more or less triangular, and are pointed downwards 

 towards the base, the extremity of the leaf being undivided and tri- 

 angular, the leaf is rundnate (runcina, a large saw), as in the Dande- 

 lion. When the apex consists of a large rounded lobe, and the divi- 

 sions, which are also more or less rounded, become gradually smaller 

 towards the base (fig. 139), as in Barbarea, the leaf is called lyrate, 

 from its resemblance to an ancient lyre.* When there is a concavity 



Fig. 139. Lyrate leaf of Barbarea. 



Fig. 140. Panduriform, a fiddle-shaped leaf of Rumex pulcher. 



Fig. 141. Compound leaf; ternate, the leaflets being obcordate. 



Fig. 142. Compound leaf; quaternate, the leaflets being rotundate-cuneiform, or wedge- 

 shaped with rounded apices. 



Fig. 143. Two-lobed leaf, somewhat cordate at the base, emarginate, and mucronate. 



Fig. 144. Palmate leaf, the divisions acute and serrated at their margins. Radiating vena- 

 tion. 



* Under the term lyrate, some include compound pinnate leaves in which the several pinnse 

 are united at the apex of the leaf, and the others become gradually smaller towards the base. 



