raunkiaer's life forms 31 



longs. We shall v\vn be able in the majority of cases to obtain 

 the correct size without the assistance of the plate. A plant 

 whose leaves are distributed between nanophylls and micro- 

 phjdls may be regarded as a nano-microphyll, etc. If we wish 

 in a given case to determine exactly where a leaf belongs, we can 

 make use of paper whose weight per square centimeter is known 

 and from it cut out the leaf area, weigh the same and compare 

 its weight with the weight of same paper which corresponds to 

 the limit between microphyll and mesophyll; namely, 2025 

 sq. mm. 



As to the advantages of this method, I would say that in this 

 way we can easily interpret climatic factors in terms of leaf- 

 size, and we can compare conditions in two climatic areas whose 

 responses to climate differ in some outstanding particular, such as, 

 for example, that of bud protection, below the surface of the 

 substratum (in life-form), and demonstrate that the climatic 

 differences give a variation in leaf-size. We may also note 

 whether the variations exist when we investigate the vegetation 

 of countries with sijuilar climates but w^ith flora composed of 

 different species. 



We may investigate by this method formations w^hich vary 

 in different areas but in which the organisms are so similar that 

 the various formations have assumed a common aspect, and we 

 here possess the means of determining to what extent the re- 

 action is different in so far as its character is revealed in leaf- 

 size. I shall endeavor to illustrate this by a few examples, com- 

 paring several European evergreen scrub formations. These 

 examples are taken from those I have investigated by statisti- 

 cal (valence) method. In a given formation it is necessary to 

 determine first the degree of frequency of a species and use this 

 index as a foundation for the comparison, and thus significant 

 and reliable results may be obtained. 



As examples of evergreen shrub formations, I have chosen: 

 (1) a west Jutland heath — Calluna vulgaris formation, (2) a 

 marquis or thicket (Garigue) in southern France, Erica multi- 

 flora formation, (3) a mountain maquis in northeastern Spain, 

 Arbutus iinedo and Quercus coccifera formation, (4) a thyme 



