raunkiaer's life forms 27 



In general it is sufficient to observe the outstanding character 

 without proceeding with a statistical study of it as related to 

 the environment. A statistical investigation for the purpose 

 of ascertaining the importance of a single character, to be suc- 

 cessful, must be directed so as to treat the xeromorphic charac- 

 ters of various plant societies in exactly the same way. 



A comparison of a series of evergreen phanerophytic commu- 

 nities, such as a tropical rain forest, a mesophytic tropical ever- 

 green forest of the West Indies, and a thicket (Maquis) of the 

 Mediterranean region reveals among the various adjustments a 

 decrease of the transpiring surface, a decrease in leaf-size, as one 

 of the main features. This character not only plainly evident^ 

 but also comparatively easy t'o measure, and is readily accessible 

 for the application of statistical methods. And yet difficulties 

 are encountered in such an investigation. 



What shall be the units measured? The leaves, the physiol- 

 logical units that are present, correspond to the morphological 

 units, but shall we compare the simple leaf with the leaflet of 

 a compound leaf or with the entire leaf? If we compare 

 the simple leaf with the compound leaf of the same life-form 

 in the same community, as for example, the canopy of the 

 East Indian deciduous phanerophyte forest, we find that 

 the compound leaf generally is mudh larger thap the simple 

 leaf, and belongs to higher "size-class" than the latter, hence 

 the leaflet is more nearly comparable in size to the simple leaf, 

 even if some of the leaflets are somewhat smaller. Conse- 

 quently, it naturally follows that the leaflet is to be regarded 

 as the biological unit rather than the compound leaf. 



A still greater difficulty is encountered in dealing with the 

 lobed leaf, which presents all variations from the simple to the 

 compound, but we shall regard the lobed leaf without further 

 discussion as a simple leaf. Neither is it as easy as it might 

 appear to determine the proper place of lacerated and dissected 

 leaves: in some cases it seems natural to regard the whole leaf 

 as a unit, in other cases a single lobe, and in still others a series 

 of lobes seem to constitute the unit, which must be compared 

 with the simple leaf. 



