3] PHYSIOLOGICAL REACTIONS 95 



hydrophytes, examples from areas in the main cUmatic behs whose 

 land-vegetation is described in Chapters XII-XIV are as follows, 

 in round figures : 



(i) Temperate — phanerophytes 15, chamaephytes 2, hemicrypto- 

 phytes 49, geophytes 22, therophytes 12 ; 



(ii) Arctic — phanerophytes i, chamaephytes 22, hemicryptophytes 

 61, geophytes 15, therophytes i ; 



(iii) Tropical (moist) — phanerophytes 61, chamaephytes 6, hemi- 

 cryptophytes 12, geophytes 5, therophytes 16 ; 



(iv) Tropical (arid) — phanerophytes 9, chamaephytes 14, hemi- 

 cryptophytes 19, geophytes 8, therophytes 50. 



With the above it is interesting to compare the ' normal ' spectrum 

 for the world as a whole, which is claimed to be : phanerophytes 

 46, chamaephytes 9, hemicryptophytes 26, geophytes 6, therophytes 



13- 

 Altogether it may be concluded that such life-form spectra can 



give a useful if generalized impression of the biological effects of 

 climatic features and hence help characterize the various phytogeo- 

 graphical regions. But dealing as they do with wide categories, 

 and with flora rather than vegetation (that is, with the different 

 kinds of plants inhabiting an area regardless of their abundance and 

 relative importance), they are no adequate substitute for more 

 thorough description with structural details, precise naming, and, 

 wherever possible, good illustration. Thus, for example, a small 

 group of species or even a single species may dominate and largely 

 characterize a plant community or sometimes a whole region, and 

 yet scarcely ' tell ' in the spectrum. This, however, is an objection 

 to the spectrum method of counting species rather than to the life- 

 form classification itself. 



Further Consideration 



The principles of plant physiology can readily be acquired from W. O. 

 James's An Introduction to Plant Physiology, fifth edition (Clarendon 

 Press, Oxford, viii + 303, 1955) or, in more detail, from such a text as 

 B. S. Meyer & D. B. Anderson's Plant Physiology, second edition (Van 

 Nostrand, New York etc., pp. viii + 784, 1952). 



More details and examples of structural ' adaptations ' that apparently 

 enable plants to maintain or extend their geographical ranges, may be 

 gained from almost any good modern work on structural botany, or from 

 G. Haberlandt's classic Physiological Plant Anatomy, translated by M. 

 Drummond (Macmillan, London, pp. xv + 777, 1914, reprinted 1928). 



