64 



MORPHOLOGY OF LEAVES AS FOLIAGE. [~LES5ON 9. 



Sugar-Maple and the Button wood (Fig. 50) have palmately five- 

 lobed leaves ; the Soft White-Maple palmately Jive-parted leaves; and 

 so on. And in the other sort, the Post-Oak has pinnately seven- 

 to nine-lobed leaves ; the Red-Oak commonly has pinnately seven- to 

 nine-cleft leaves, &c., &c. 



162. The divisions, lobes, &c. may themselves be entire (without 

 teeth or notches, 156), as in Fig. 118, 122, &c. ; or serrate (Fig. 

 124), or otherwise toothed or incised (Fig. 121) ; or else lobed, cleft, 

 parted, &c. : in the latter cases making twice pinnatifid, twice pal- 

 mately or pinnately lobed, parted, or divided leaves, &c. From these 

 illustrations, the student will perceive the plan by which the bota- 

 nist, in two or three words, may describe any one of the almost 

 endlessly diversified shapes of leaves, so as to convey a perfectly 

 clear and definite idea of it. 



163. Compound Leaves. These, as already stated (155), do not 

 differ in any absolute way from the divided form of simple leaves. 

 A compound leaf is one which has its blade in two or more entirely 

 separate parts, each usually with a stalklet of its own : and the stalk- 

 let is often jointed (or articulated) with the main leaf-stalk, just as 

 this is jointed with the stem. When this is the case, there is no 



doubt that the leaf is compound. But when the pieces have no 

 etalklets, and are not jointed with the main leaf-stalk, the leaf may 

 be considered either as simple and divided, or compound, according 

 to the circumstances. 



FIG. 126. Pinnate with an odd leaflet, or odd-pinnate. 127. Pinnate with a tendril 

 128. Abruptly pinnate leaf. 



