66 THE WORLD OF LIFE 



which they abound. Thus the Urticacese include not only 

 nettles, hops, and allied plants, but mulberries, figs, and bread- 

 fruit trees. Even Avith so much identity in the natural orders, 

 there is often a striking dissimilarity in the plants of distinct 

 or remote areas, owing to the fact that the genera are very 

 largely different, and that these often have a very distinct 

 facies in leaf and flower. Thus, though the Myrtacese are 

 found in hot or warm countries all over the world, the Euca- 

 lypti, so abundant in Australia, give to its vegetation a highly 

 peculiar character. So the Onagracese are found in all the 

 temperate regions, yet the Fuchsias of South-temperate 

 America are strikinoly different from the Willow-herbs of 



CD «- 



Europe or the CEnotheras of ^^Torth America ; and there are 

 thousands of equally characteristic genera in all parts of the 

 world. 



In Mr. Hemsley's elaborate table of the General Distribution 

 of Vascular Plants, he gives, in Central America, the number 

 of species of each order in Nicaragua, Costa Rica, and Panama 

 respectively, these three states constituting the tropical section 

 of the whole area, and the same for six subdivisions of the rest 

 of the area. But the numbers added together will give more 

 than the actual number of species in the combined flora, be- 

 cause an unlvnown portion of the species will be found in two 

 or three of these divisions. But he gives the total numbers 

 for these three states and also for the remainder of the nine 

 areas. He also gives the numbers which are '^ endemic " in 

 these two groups of areas separately and in the whole flora ; I 

 have therefore been able to ascertain the proportion which the 

 endemic bear to the total in Mexico and Guatemala, which I 

 find to be as 3 to 4 verv^ nearly, so that by deducting one-fourth 

 of the sum of the species in these areas I obtain the number 

 existing in the combined area. But as it is known that in the 

 tropics species have a less range than in the temperate zone, 

 I deduct one-fifth in the case of the three tropical areas, which 

 will, I believe, approach very nearly to the actual number of 

 species in the combined floras as given in the following table. 



