1G4 Progress of Foreign Science. 



British Isles . as 1 to 3.6 



North America . „ 1 .? 4.6 



Under the frozen zone, in Lapland „ 1 ,, 2.8 



Iceland „ 1 „ 2.8 



As the monocotylcdonous love humidity, they are more nu- 

 merous on the British islands, and rarer in Egypt and on the 

 arid mountains of Caucasus. 



In the most fertile portion of Europe in the centre of the 

 temperate zone an extent of country of 30,000 square leagues 

 nourishes nearly 6,000 species of plants, of which 2,200 are 

 acotyledonous or cryptogamous, and 3,800 phanerogamous. 

 Among the latter there is nearly 500 compositor, 300 gratnincce, 

 (exclusive of the cyperoidece and joncacecs,) 250 leguminous, 

 and 200 cruciform, .but only 70 amcntacecB, 50 etiphorbiacece, 

 and 25 malvacccB. The great families form from \ to -^^j, the 

 small under 3!^ of the total mass of the phanerogamous; this is 

 the mean state of vegetation in Europe in fertile districts between 

 42° and 50°of N. latitude. We may consider the ciphers indicated 

 in the following table as the co-efficients of each family, for by mul- 

 tiplying the number of phanerogamous plants of the temperate 

 zone of Europe by 0.75, or 0.53, Ave find the number of species 

 which compose the families of the graminese, or the cruciform. 



Explanation of the Signs. — ^ the denominator of the fraction 

 diminishes from the equator, towards the north pole ; j^ the de- 

 nominator diminishes from the north pole towards the equator 



