STRUCTURAL BOTANY. 49 



creasing in size toward the base (PI. II., 30) ; runcinate^ 

 those with rather sharp lobes pointing toward the stem 

 or branch, or downward. (PI. II., 2.) 



Palmately -cleft leaves are sometimes briefly called pal- 

 mate leaves^ and a palmate leaf with the lateral lobes cleft 

 into two or more segments, is said to be 2>edate (since it 

 resembles a bu'd's foot). 



The segments of a lobed or divided leaf may be again 

 divided, parted, or cleft, and then the leaves are said to 

 be hipinnatifid, trvpinnatifid (that is, bipinnately or 

 tripinnately parted), or twice^almately, thrice-j[)almately 

 clef t^ parted^ etc. 



ft COMPOUND LEAVES. 



99, A COMPOUND LEAF is a leaf composed of two- or 

 more blades, called leaflets^ borne on a common petiole, 

 and usually supported by stalklets of their own, between 

 which and the main petiole an articulation is formed. 

 The leaflets we describe just as we do simple leaves, as 

 entire, serrate, toothed, cleft, parted, etc. 



100. Compound leaves are of two principal sorts — 

 namely, the pinnate and the pahiiate {or digitate). 



The first sort are produced when a simple leaf of 

 the pinnately-veined variety becomes compound ; they 

 have their leaflets, or pinnae, along the sides of the com- 

 mon petiole ; the second sort result from the palmately- 

 veined kind of simple leaves becoming compound ; they 

 bear their leaflets, or folioles, on the apex of the common 

 stalk. 



When the division of a simple leaf reaches the riiidrib, 

 or the top of the petiole, the leaf is said to be compound. 

 (PI. II., 6, 11.) I^ot unfrequently it is rather difficult to 

 decide, whether a leaf is simple or compound ; and we 

 may even find in different parts of the same leaf different 



