540 BOTANY 



her of identical species is not large, and there is a large proportion 

 of quite unrelated forms. In Europe the Oaks, Elms, Ashes, 

 Beeches, etc., are all different species from those in America, and 

 the latter continent shows various types, such as the Hickories, 

 Tulip-tree, and Sassafras, which are quite absent from the present 

 European flora. Among herbaceous plants the differences are per- 

 haps even more marked, for although there are many genera in 

 common, each has forms not represented in the other. Thus America 

 has no true Heaths, no Foxgloves, no Crocus, Tulip, or Narcissus. 

 On the other hand, Dicentra, Bloodroot (Sanguinaria), Mandrake 

 (Podophyllum), some of the most beautiful Orchids, like Arethusa 

 and Pogonia, Sarracenia, and many others, are quite absent from 

 Europe. 



Warm Temperate Zone. The greater part of Europe lies within 

 the northern zone, and it is only along the Mediterranean that a 

 flora characteristic of a warmer region is noted. Here we meet with 

 many types not occurring in Central and Northern Europe, and 

 equally absent from our own flora, and which are related to the 

 Asiatic and North African types. 



In Asia and America there is no break between the temperate 

 and tropical floras, as the land communication is continuous and the 

 two mingle gradually. Thus in the middle part of Japan, Bamboos 

 and Palms grow together with the northern Pines and Maples, and 

 in the Southern United States the northern Oaks and Hickories are 

 associated with Palmettoes, Magnolias, and other trees of tropical 

 affinities. The contrast between the great variety of trees in the 

 forests of Japan and the United States and the poverty in species of 

 the European forests is extremely marked. 



Tropics. It is of course in the Tropics that plants reach their 

 greatest development in number of species and individuals, but 

 within the Tropics there is great difference in different regions, de- 

 pending upon the rainfall. In the equatorial rain belt, and in other 

 regions of heavy rainfall, the country is covered with an impene- 

 trable forest in which myriads of plants are fighting for existence. 

 Every available spot is occupied, not only upon the ground, but the 

 trees are loaded down and often killed by the masses of climbing 

 plants and epiphytes which are struggling for light and air. Unlike 

 the monotonous forests of the far North, composed of a single species 

 of tree, here one is bewildered by the variety of plant-forms. The 

 tree trunks are completely hidden by the stems and leaves of climb- 

 ing plants Aroids, Rattan-palms, Leguminosse, Bignonias, which 

 ascend until their leaves mingle with those in the crown of the sup- 

 porting tree. Clinging to the trunk and branches are innumerable 

 epiphytes Ferns and Mosses, Orchids, Bromelias, Loranthaceae. 

 In the gloomy recesses of such a forest showy flowers are not abun- 



