OF PLANTS. 257 



to totally different families, assume, at least in their outward 

 appearance, similar shapes. Thus the Cactus plants of the 

 New World correspond to the leafless fleshy Spurges of the 

 torrid Africa. 



If, again, we anticipate that a greater variety of condi- 

 tions of vegetation is the cause why the variety of vegeta- 

 tion, the number of species of plants, continually augments 

 from the pole towards the equator, and that on the same 

 account the number of sociably growing plants, of species 

 which clothe great tracts in countless individual specimens, 

 also increases in the same measure, we find that we are still 

 far from being enabled to give a scientific account of the 

 matter. It seems to us wholly the result of caprice, that 

 particular plants are distributed widely over the globe, 

 while others must live cribbed in the narrowest spot, as, 

 for instance, the Wulfenia, occurring exclusively on the 

 Carinthian Alps ; that particular families, like the Composite, 

 flourish abroad over the whole earth, while others, like the 

 Peppers and the Palms, only occur between very definite 

 degrees of latitude on either side of the equator, the 

 Proteacea only in the southern hemisphere, the Cactus 

 tribe only in the western half of the earth. Just as inex- 

 plicable is the mode of distribution of the families of 

 plants. While the Palms diminish in number from the 

 equator into higher latitudes, the Composite attain their 

 highest development in the zones of mean temperature, their 

 number of species diminishes from these in both directions, 

 equally toward the equator and toward the poles; while, 

 finally, the Grasses increase constantly from the equator 

 toward the poles. 



But there yet remains to be brought forward a peculiar 

 mode of consideration, according to which the distribution 

 of the families is usually determined. 



17 



