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 ; 
(5) 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 
Parts of a model leaf 
Classes of parallel-veined leaves . 
Relation of venation to number of cotyledons 
inssee of netied-veined leaves... . . . 2 » « ‘ 
c 
Compound leaves ;—-types, dependent on arrangement of i. 
leaflets . ‘2. 
Once, twice, or three times compound. . .... .- { 
1 Illustrate by sketches if possible. 
