THE FAUNA OF " BESEBVOiB■PLANTS: , 195 



Several of the above suggested methods of colonisation of the 

 brornelias will also apply to the dissemination of the fauna, its 

 passage from plant to plant. But there are also other ways in 

 which it can be passively disseminated. For instance, brornelias 

 often grow at different levels on the same tree, and if a plant 

 be upset by any accident its contents may be spilled into others 

 growing below. In such passive ways the fauna need not only 

 descend ; it can also slowly ascend. Brornelias reproduce largely 

 by lateral budding, and the young plants grow to a slightly 

 higher level than that of their parents, and in their turn produce 

 buds which push a little higher, and so on. Each lateral bud 

 grows up through one of the interfoliar spaces of the parent 

 plant, and in so doing may carry with it some of the contained 

 water and fauna. Also the boughs and trunks to which the 

 brornelias cling grow slowly upwards and outwards, carrying the 

 epiphytes with them. Thus the Bromeliacece with their fauna 

 may climb slowly, till they are perched right aloft in the green 

 roof of the forest. 



factor in the production of the great number of endemic species in the 

 Hawaiian Islands. He distinguishes carefully the two kinds of isolation, 

 viz. (1) that due to the existence of geographical barriers, and (2) isolation 

 and segregation of forms inhabiting the same area due to difference of 

 habits. 



