LEAVES 139 



separate leaflets, is really only one leaf is shown : (1) by 

 the absence of buds in the axils of leaflets (see Fig. 82) ; 



(2) by the arrangement of the blades of the leaflets hori- 

 zontally, without any twist in their individual leaf-stalks ; 



(3) by the fact that their arrangement on the midrib does 

 not follow any of the systems of leaf ; arrangement on the 

 stem (Sect. 149). If each leaflet of a compound leaf should 

 itself become compound, the result would be to produce 

 a twice compound leaf. Fig. 113 shows that of an acacia. 

 "What would be the appearance of a thrice compound leaf ? 



148. Review Summary of Leaves.^ 

 Parts of a model leaf J 2. 



Classes of netted-veined leaves 



Classes of parallel-veined leaves 



3. 

 2. 

 2. 



Relation of venation to number of cotyledons . . . . ^ 



Compound leaves ; — types, dependent on arrangement of J 1. 

 leaflets | 2. 



Once, t-wice, or three times compound .... 

 1 Illustrate by sketches if possible. 



