22 SHAPE OF LEAF [CH. 



of the numbers in Fig. 6, and it is advisable to observe 

 these terms and consistently use them for such cases. 



Leaf-outlines, however, are rarely so simple as this, 

 and one of the commonest modes of departure from the 

 fundamental form is due to the base or apex (or both) 



Fig. 6. Outline-forms of simple leaves. 1 acicular; 2 linear; 

 3 oblong; 4 oval; 5 sub-rotund. The petiole and base to the left. 



of the lamina being broader or narrower than in the 

 geometrical figure which the outline as a whole suggests. 

 Thus, the leaves of most Grasses taper too much and too 

 gradually to be called simply linear ; those of the Sallow 

 are too broad at the base to be termed purely oval ; and 

 those of Salix herbacea though often nearly rotund are 

 not so exactly so as the type chosen above. 



To provide for these and similar cases, which occur 



