GENEBAL MOEPHOLOGY OF THE PLANT 81 



if there are more than seven {fig. 158), as in many species of 

 Lupin. The term digitate is generally used when the segments 

 of such a leaf are long and narrow. 



2. INSERTION AND AKEANGEMENT OF LEAVES. 



(1) Insbetion.— The point by which a leaf is attached to the 

 stem or branch is called its insertion. Leaves are inserted on 

 various parts of the stem and branches, and receive different 

 names accordingly. Thus the first leaves which are developed 

 are called cotyledons {fig. 16, e, c). The cotyledons are usually 

 very different in their appearance from the ordinary leaves 

 which succeed them. Leaves are called radical when they arise 



Fig. 161. Fig. 162. 



Fig. 161. Whorled leaves of a species of Galium. Fig. 162. Decussate 



leaves of IHmelea decussata. 



at, or below, the surface of the ground, and thus spring apparently 

 from the root, but really from a shortened stem, or crown of the 

 root, as it is commonly called. Leaves are thus situated in what 

 are termed acaulesoent plants, such as the Dandelion and Prim-. 

 rose. The leaves which arise from the main stem are called 

 cauline ; those from the branches ramal. 



(2) Arrangement or Leaves on the Stem, or Phyllo- 

 TAXis. — The term phyllotaxis is used in a general sense to 

 indicate the various modes in which leaves are arranged on the 

 stem or branches. There are two main types of such arrange- 

 ment, depending on whether a single leaf or more than one is 

 produced at a node. In the former case the leaves are scattered 

 or alternate ; in the latter, they are said to be whorled {fig. 161). 

 The leaves constituting a whorl are usually placed symmetrically 



VOL. I. e 



