FOLIAGE LEAVES. 



389 



in holding it in the expanded position. The mechanical tissue in the 

 framework alone could not support the leaf. Turgescence of the meso- 

 phyll is needed in addition. 



757. Cut or lobed leaves.— In many leaves, the indentations 

 on the margin are few and 

 deep. Such leaves pre- 

 sent several lobes the pro- 

 portionate size of which 

 is dependent upon the 

 depth of the indentation 

 or "incision." Several 

 of the maples, oaks, 

 birches, the poison iv}-, 

 thistles, the dandehon, 

 etc., have lobed leaves. 

 Where the indentation 

 reaches to or very near 

 the midrib the leaf is 

 said to be cut. A study 

 of various leaves will 

 show all gradations from 

 simple leaves with jjlane edges to those which are cut or divided, as 

 in compound leaves, and the lobes are often variously indented. 



758. Divided, or compound leaves. — The rose, sumac, elder, 

 hickory, walnut, locust, pea, clover, American creeper, etc., are 

 examples of divided or compound leaves. The former are pin- 

 na tely compound, and the latter are palmately compound. The 

 leaf of the honey-locust is twice pinnately compound or bipin- 

 nate, and some are three times pinnately compound.* It is 



Fig 4.vi. 

 Lubed leaves of oak forming a m(jsait 



* Some of the different terms used to express the kinds of compound 

 leaves are as follows : 



Uni foliate (for a single leaflet, as in orange and lemon where the com- 

 pound leaf is greatly reduced and consists of one pinna attached to the 

 petiole by a joint). Bijolititc for one with two leaflets; trijoUalc for one 

 with three leaflets, as in the clo\-er; plurijoliale for many leaflets. Odd 

 pinnate for a p>innate leaf w-ith one or more pairs of leaflets and one odd 

 leaflet at the end. 



