70 OUTLINE OF PLANT GEOGRAPHY 



zones passing through all degrees of temperate and arctic climate 

 to the regions of everlasting snow and ice. 



The temperate zone begins at about 5,000 feet elevation, but 

 the distribution of the temperate flora is controlled both by eleva- 

 tion and moisture. In the eastern parts of the Himalaya are 

 regions of excessive rainfall, reaching a maximum in the lower 

 ranges about the head of the Bay of Bengal. Westward there is a 

 marked diminution in rainfall, and a corresponding falling off in 

 the luxuriance of the forests. This is true also on the northern 

 slopes, which descend to the great Tibetan highlands, among the 

 most desolate and forbidding regions of the world. 



The western Himalayan temperate forests have much in common 

 with those of Europe. Oaks, ashes, elms, poplars, maples and 

 other familiar genera, predominate, giving place at higher eleva- 

 tions to willows, alders and other sub-arctic and arctic forms, 

 which are replaced at still higher altitudes by a genuine arctic- 

 alpine flora which reaches to the limits of vegetation. 



Coniferous trees, pines, firs, larch, yew and cypress are common, 

 and the Atlas and Lebanon cedars are represented by the beautiful 

 Deodar. Of the pines, Pinus longifoHa, and P. excelsa are the most 

 important. Walnuts, horse-chestnuts and plane-trees are rem- 

 iniscent of the forests of Asia minor and the Balkans. 



Eastward, as we have seen, the rainfall increases rapidly, and 

 this is accompanied by a decided change in the flora. Conifers 

 are much less prominent, and the European element is to a great 

 extent superseded by species related to those of Japan and China 

 which in turn have a strong relationship with many American 

 species. A forest of this type may be seen in the neighborhood 

 of Darjiling, whose unrivalled panorama of the main range of the 

 Himalaya is world famous. 



Darjiling lies at an elevation of about 7,000 feet, and has an 

 annual rainfall of 120 inches, so that the forest is a very luxuriant 

 one. It is a mixed forest of deciduous and evergreen angiospermous 

 trees. Oaks are perhaps the most abundant trees, but with these 

 are associated maples, laurels, birches, chestnuts, and especially 

 characteristic are several species of magnolias and tree rhododen- 

 drons. Magnolias are quite absent from Europe and western Asia, 

 but a conspicuous feature of the eastern Asiatic and North Amer- 

 ican floras. Both Magnolia and Rhododendron comprise some 



