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. 1 



f 1 - 



Parts of a model leaf ... Jo 



Classes of netted-veined leaves 



Classes of parallel-veined leaves 



Relation of venation to number of cotyledons . . . . J 

 * I 



Compound leaves ; types, dependent on arrangement of Jl. 



leaflets 1 2. 



Once, twice, or three times compound .... 

 1 Illustrate by sketches if possible. 



