Chapter V 



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Types of Areas 



In reality, there are no true cosmopolites, i.e., species inhabiting 

 the entire globe from pole to pole, at least not among the higher plants. 

 As Alphonse de Candolle (1855) pointed out, such species cannot 

 exist. There are species distributed from the arctic through the tem- 

 perate zone and then reappearing in the southern hemisphere; there 

 are also species distributed throughout all the tropics and even con- 

 siderably beyond them. But there are no species, at least no low 

 elevation species, distributed on the equator and at the same time reach- 

 ing nearly to the two opposite poles. This is due to the great differ- 

 ences in climatic and edaphic conditions, and holds true both for 

 species naturally distributed and for those which have accompanied 

 man. Hence, cosmopolitanism, in the absolute sense of this word, does 



Fig. 6. — Distribution of species of Celsia in southern Europe and northern Africa; 6i, 

 C. ramosissima; 62, C. Ballii; 63, C. longirostris; 64, C. cretica; 65, C. pinnatisecta; 66, C. 

 lyrata; 67, C. laciniata; 68, C Barnadesii; 69, C. Battandieri; 70, C. maroccana; Ti, C. 

 zaiamensis; y2, C. Faurei; yj, C. commixta; y^, C. belonicifolia. (After Murbeck). — 65,74 

 included areas; 63, 64, 69, 70, 72 overlapping areas; 62, 68, 71 separate areas; 61, 67, 73 

 contiguous areas. 



not exist, and if we use this term, it is only in a relative and approxi- 

 mate sense. The number of species occupying as much as half of the 

 earth's surface is very limited and does not exceed 20 or 30 species. 

 De Candolle could enumerate only 18 such species, and even if we 

 assume that closer acquaintance with the distribution of plants would 

 show the inaccuracy of this figure and that it should be doubled or 

 trebled, the number of such species is nevertheless insignificant. Even 

 the total number of species occupying one-quarter of the earth's sur- 

 face is insignificant in comparison with the total number of species. 

 According to de Candolle, it is not over 200 (to be accurate — 116), 

 which amounts to only o.ooi per cent of the total number of flowering 

 plants known in his time. 



