For the Javanese mountain plants, all growing on separated volcanic peaks, it has been found before that to grow on a mountain there is for each species a critical altitude necessary of the total height (elevation) of the peak or mountaincomplex. This is best elucidated by an example: Albizia lophantha (montana) is found in Java from 1100-3100 m, but only on mountains of which the summit reaches at least 2500 m altitude. This means that it is not found on mountains of 2400 m summit height or lower, although it may descend on mountains of 2500 m summit height and higher as low down as 1100 m altitude. The elevation effect is calculated in this case as 2500 minus 1100 = 1400 m.