DISSEMINATION OF SEEDS. 135 



consisting of rich soil from the forests through which the 

 stream flows, seeds germinate and, as the depth of soil 

 increases, the plants springing from these seeds flourish 

 with unwonted vigor hundreds of miles from the places 

 where these seeds were formed and ripened. In some 

 cases they have been seen covered with a growth of green 

 bushes and small trees. 



Rivers running east or west cany seeds and extend 

 the limits of species, while those running north or south 

 are not so likely to carry the seeds to a climate suited to 

 their development. 



Sir Charles Lyell tells us, in his Geology, that, among 

 the Moluccas, floating islands, similar to the river- rafts 

 before-mentioned, are often seen. On these, mangrove 

 trees as well as undershrubs and a multitude of smaller 

 plants flourish. Similar rafts with trees on them have 

 been seen after hurricanes in the neighborhood of the 

 Philippine Islands. 



DISSEMINATION BY ICEBERGS. 



Icebergs are very often loaded with debris in which 

 earth and seeds may be found. The seeds germinate and 

 plants begin to grow in the alluvial soil of the iceberg, 

 sometimes becoming of considerable size. If the ice- 

 berg, driven by currents and winds, is at last stranded on 

 some distant shore, these wandering plants may become 

 permanently established. 



DISSEMINATION BY OCEAN-CURRENTS. . 



Ocean-currents, too, are efficient carriers of plants and 

 of seeds. The seeds of grasses and sedges are often 

 enveloped in chafly glumes ; thus protected they may be 



