LIFE FORMS AND SYNECOLOGICAL UNITS 299 



Central Europe lies in the midst of the hemicryptophyte region of 

 the northern hemisphere; that is, hemicryptophytes exceed in number 

 of species all other life forms. Central Switzerland, between lakes 

 Geneva and Constance, with 1,700 seed plants, may be taken as 

 typical of such a hemicryptophyte climate in Europe (Table 34); 

 and with it may be compared Connecticut, in North America, with 

 1,400 species (Ennis, 1928). In both areas ruderal immigrants have 

 increased the number of therophytes. The spectrum of the exclusively 

 native species of the Paris basin also shows a hemicryptophyte climate, 

 according to Allorge (1922). 



In the north and in the high Alps along with the hemicryptophytes 

 the chamaephytes come more and more into their own. Thus Spitz- 

 bergen has 22 per cent chamaephytes but only 2 per cent therophytes 

 (Koenigia islandica and Gentiana teyiella). The summer heat is not 

 sufficient to ripen seed every year, and young seedlings are likely to be 

 killed by frost. The spectrum of the life forms of the 260 flowering 

 plants which make up the flora above the snow line (2,600 to 3,100 m.) 

 in the Alps shows somewhat similar conditions (Table 34). At an 

 altitude of 3,340 m. the percentage of chamaephytes has risen to 31. 



The spectra of warm, dry regions are radically different from these, 

 as shown by examples given by Raunkiaer. The flora of Cyrenaika in 

 northern Africa, and of Death Valley, California, show comparable 

 spectra. In contrast with the paucity of phanerophytes in these arid 

 regions are the conditions in the rainy tropics, as exemplified by the 

 spectrum from the Seychelles (Table 34). 



Thus the spectra of life forms give a direct impression of the climatic 

 peculiarities of the various phytogeographic regions of the earth. 

 Regions with similar biological spectra may be joined by a line, the 

 so-called "isobiochore. " 



Ecological Significance of Life Forms. — Raunkiaer's life forms in 

 their present arrangement are of use also in the broad ecological 

 characterization of plant communities. Without going as far as Vahl 

 (1913), Gams (1918, 1927), and other writers, who base the classifica- 

 tion and nomenclature of plant communities upon life forms, ^ it is at 

 least desirable to give them a definite place along with the floristic 

 differentiation and delimitation of communities. This use is partic- 

 ularly desirable in distant parts of the earth where the flora is little 

 known. On a journey of investigation many species cannot be identi- 

 fied immediately, but they may be classified according to life forms, and 

 thus a preliminary picture of the ecological character of the plant 

 communities may be obtained. Life forms should not be neglected in a 



^ Vahl (1913) speaks of Chamaephytae, Cryptophytae, etc. 



