The Problems of Plant Distribution 261 



types as buttercups, strawberries, violets, brambles, 

 primroses, gentians, and others obviously of north- 

 ern origin, and quite unrelated to any of the plants 

 of the adjacent lowlands. These isolated waifs, in 

 the course of ages, and under the milder conditions 

 prevailing, even on the high mountains in the tropics, 

 have become specifically changed, but have neverthe- 

 less retained their generic characters. 



Some of the high, isolated peaks of the tropics 

 afford striking instances of the change in vegeta- 

 tion due to altitude. The great volcanic mass of 

 the Gedeh in Western Java, is an especially good 

 example of this. This mountain rises to a height 

 of 10,000 feet, and lies but a few degrees from 

 the equator in a region of very heavy rainfall. As 

 one ascends from the luxuriant tropical vegetation 

 of the lowlands at the base of the mountain, a change 

 is very soon apparent. At about 4,500 feet (1,400 

 m.) the temperature has fallen many degrees, and 

 although the heavy rains and almost constant clouds 

 and mist promote an extraordinarily luxuriant for- 

 est growth, many of the strictly tropical types like 

 palms and bamboos have nearly disappeared, and a 

 number of northern types become common. Oaks, 

 chestnuts, and maples occur, and several trees be- 

 longing to genera common in our Southeastern 

 States are met with. The loftiest tree of this moun- 

 tain forest (Altingia cxcelsd) is related to the sweet 

 gum (Liquidambar) of the Eastern United States; 

 and species of Nyssa, like the pepperidge or " sour 



