94 



INTRODUCTION TO PLANT GEOGRAPHY 



[chap. 



Further categories may, if desired, be added to the above system 

 — such as epiphytes growing on trees etc. Moreover, refinements 

 may be used such as the subdivision of phanerophytes into nano- 

 phanerophytes (shrubs) in w^hich the renewal buds he less than 2 metres 

 above ground, microphanerophytes (small trees) in which they lie 

 at a height of from 2 to 8 metres, the taller mesophanerophytes 

 (8-30 metres), and the still taller megaphanerophytes (above 30 metres) ; 

 also phanerophyta scandentia (lianes) which are woody climbing 

 plants whose renewal buds pass the unfavourable season high above 

 the ground. 



Fig. 24. — Diagrams illustrating some Raunkiaer life-forms. A, a creeping 

 chamaephyte; B, a rosette hemicryptophy te ; C, a tufted hemicryptophyte ; D, 

 a bulb geophyte; E, a rhizome geophyte; F, a therophyte. (After Braun- 



Blanquet.) 



The values of this system are relative, its applications limited. 

 Being based on wide life-form categories, it certainly cannot take 

 the place of detailed description of vegetation including naming of 

 the main species concerned, which alone will indicate to the qualified 

 reader the precise nature of each named species and, through these, 

 reveal much concerning the community itself. Its use is, moreover, 

 limited in arctic and alpine regions where the success of a particular 

 plant in life is apt to depend not so much on its adaptation to a 

 rigorous winter as on its adjustment to the very short and cool 

 summer. Nevertheless, in the hands of the student who is statistic- 

 ally but perhaps not taxonomically minded and trained, not wanting 

 or able to name specifically the plants concerned, this system is 

 useful in giving a fair analysis of the components of a community 

 or flora in terms of the representation of each life-form. 



Such an analysis is usually expressed as a ' biological spectrum ', 

 indicating the percentage of the total flora belonging to each of the 

 life-forms involved. Considering only vascular plants and excluding 



