92 introduction to plant geography [chap. 



Classification by Life-forms 



The ' life-form ' or ' growth-form ' of a plant is the form which 

 its vegetative body produces as a result of all the life-processes, 

 including those that are affected by the environment within the 

 plant's life-time and are not heritable. Although a plant's life-form 

 is among its most striking characteristics, it may be of a rather fickle 

 nature. Thus different individuals of the same species can some- 

 times belong to different life-forms, for example when they have 

 been grown in different environments ; for under any particular 

 life-form are merely grouped together those plants which, in their 

 entirety, show similar morphological adjustments. Life-forms may 

 accordingly give a fair indication of environmental impress, or at 

 least tell us something about local conditions. 



Although the description of vegetation in terms of life-forms is 

 widely imprecise, and classification by them is inadequate for our 

 ultimate purpose, nevertheless it is a part of common parlance and 

 can be of some value. Its use goes back at least to the times of 

 the ancient Greeks, who classified plants into trees, shrubs, herbs, 

 etc., which are among the most obviously differing life-forms. Even 

 nowadays to the general geographer or other non-biologist the species, 

 etc., making up plant communities are often less significant than the 

 prevalent life-forms. These last may yet be of importance in two 

 allied biological fields, namely, plant sociology, where consideration 

 of life-forms may help in the description of the structure of the 

 communities that are the main subject of study, and ecology, where 

 mention of the predominant life-form is often sufficient to give some 

 idea of the local environment. 



In spite of the limitations mentioned above, there is one particular 

 system of life-forms which as plant geographers we may find useful, 

 although it suffers from rather difficult Greek terminology. As 

 originally elaborated by the late Professor C. Raunkiaer of Denmark 

 and usefully modified by, among others. Dr. J. Braun-Blanquet of 

 Montpellier, this system lays stress primarily on the adjustment of 

 the plant to the unfavourable season, and particularly employs the 

 position of the perennating^ buds relative to the soil surface in 

 attempting to classify together plants of similar habit. The result is a 

 series of life-forms that is especially interesting to the more statistic- 

 ally minded among us, the main categories of which are as follows : 



^ Perennation is the act of tiding over an unfavourable period, such as a cold 

 winter or a dry summer. 



