LECT. IX.] LEAVES. 481 



gina superior), or face of the leaf; the latter, 

 which has of course the opposite direction, is 

 termed the under disk (pagina inferior)) or back 

 of the leaf: but, as I remarked with respect to 

 the footstalk, these distinctions of surface are not 

 universal, for we meet with some leaves which 

 stand vertically on the branches and have both 

 surfaces alike*. That part of the leaf d. d., which is 

 next to the footstalk or to the point of attachment, 

 is always considered as the base ; and the part e., 

 which is directly opposite, the apex ; whatever may 

 be the shape of the leaf. The line e.f. d. d.f. e. 

 forming the contour of the leaf, is named the 

 margin. The angle which the leaf or its footstalk 

 forms at its point of attachment with the stem, 

 or the branch, is termed its axilla. 



Leaves are either Simple, consisting of one 

 expansion only, with or without a footstalk, 

 as those of the Lilac, the Apple tree, the Nettle, 

 Urtica dioica, and many other plants; or Com- 

 pound, consisting of several distinct expansions, 

 with or without distinct footstalks united to- 

 gether on one common footstalk, as those of 



* Mirbel considers these as transformed footstalks. He re- 

 marks, speaking of the Acacia of New Holland, " A mesure 

 " que les folioles disparaisserit, les petioles changent visible- 

 " ment de forme et de structure. La plupart s'elargissent vers 

 " les deux bouts, a la maniere d'un fer de lance." Element de 

 Phys.veg. 1. 149. 



VOL. I. I I 



