THE LEAF. 



31 



they extend quite to the midrib, the leaf is divided ; and thus 

 a single leaf, or one with a lamina in a single piece, is con- 

 verted into a compound leaf— that is, one with the blade 

 divided into several parts (Fig. 40). Each of the divisions is 

 called a leaflet. 



11. Corresponding to the pinnate and palmate type of vena- 

 tion, there are pinnately and 



palmately compound leaves. 

 Tiie pinnate leaves have the 

 leaflets or pinnae arranged on 

 each side of the rachis. If the 

 leaflets are in pairs through- 

 out, the leaf is said to be 

 abruptly pinnate (Fig. 41) ; 

 if a single leaf terminates the 

 rachis, the leaf is said to be 

 odd-pinnate (Fig. 40). Pal- 

 mate leaves (sometimes called 

 digitate) have the leaflets 

 borne on the extreme end of the leaf-stalk (Fig. 42). 



12. The primary divisions of the blade may be again divided, 

 which is expressed by the terms bi-pinnate (Fig. 43), or tri- 

 pinnate (thrice divided). ^Vhen the leaf is several times 



Fig. 42. 



Fig. 43. 



Fig. 44. 



Fig. 45. 



compound, it is said to be de-compound. Of numerous 

 other forms not yet mentioned, the following are conspicuous. 

 Perfoliate (Lat. per, through ; folium, leaf), in which the stem 



