568 DISTRIBUTION OF CEREAL GRAINS. 



colonized by Europeans. Millet of different kinds is met with in the 

 hottest parts of Africa, in the south of Europe, in Asia Minor, and in 

 the East Indies. Henslow gives the folio whig table to show the range 

 of Wheat and Barley, and the mean temperature required for them: 



Winds, water, and animals, are also instrumental in disseminating 

 plants. Many seeds with winged and feathery appendages are easily 

 wafted about; others are carried by rivers and streams, and some can 

 be transported by the ocean currents to a great distance, with their 

 germinating powers unimpaired. 



2 GENERAL AND ENDEMIC DISTRIBUTION OF PLANTS. 



1143. While some plants are generally diffused, it is found that the 

 different quarters of the globe are each characterized by more or less 

 distinct floras. Europe, Asia, Africa, North America, South America, 

 and Australasia, may be regarded as separate provinces of the vege- 

 table kingdom, possessing species, genera, and families of plants, which 

 give to each division its distinctive features. Humboldt and Bon- 

 pland, in their travels in equinoctial America, did not see an exogen- 

 ous plant which was found equally in the New and the Old World ; 

 the only plants which they discovered common to both being some 

 grasses and sedges. Among 4,160 species met with in New Holland 

 by Brown, 166 only were to be found hi Europe. 



1144. Some plants live in society, occupying exclusively large tracts 

 of ground, from which they banish all other vegetables. These are 

 called by Humboldt Social plants. They give a peculiar feature to the 

 countries and districts in which they grow. To this class belong many 

 species of Seaweed in the ocean; Cladonias and Mosses in the waste 

 levels of Northern Asia; Grasses (Bamboos), and some Cactuses, Man- 

 groves, and Avicennias in tropical countries; Ferns in the South Sea 

 Islands; Banksia speciosa in New Holland; Cinchonas in certain parts 

 of South America; Coniferous trees and Birches in the Baltic and 

 Siberian plains. 



