COLONISATION BY OTHER METHODS. 6 1 



their leaves for colonisation. In the first, Asplenium 

 bulbiferuvi^ the leaves carry on their margins numbers 

 of little fern-buds, which eventually fall off and take 

 root (cf Sediiui^ v.s.); in the second, A. rhizophyllum, 

 the tip of the leaf dips into the soil and there develops 

 a root from which a new fern is formed. This last, 

 therefore, acts exactly after the manner of a Bramble, 

 though it is the leaf and not the branch which 

 colonises. 



There are but few examples of roots being used for 

 propagation. It is, of course, a special characteristic of 

 roots not to produce either leaves or buds, yet there are 

 many exceptions. The China Grass or Rami {Boehuieria 

 nived) is multiplied by dividing the roots, and Crab 

 Apples, Medlars, Roses, Azalias, and of course the Dahlias, 

 may be grown from pieces of root sometimes only two 

 inches long. In fact Goebel has recently shown 

 that the root itself may change into a foliage stem 

 in the case of two ferns, Platycerium and Diplazium 

 {^Asplenhnn esailentuiii)^ and in Listera cordata, Neottia 

 and Anthurium. 



The Banyan and Mangrove send down vertical roots 

 from their horizontally spreading branches ; and these 

 roots become supporting trunks, and enable the tree to 

 extend its area very greatly. One Banyan, in Cejdon, 

 forms a grove said to be capable of sheltering 5000 men. 

 The Mangrove is of economic importance on the muddy 

 foreshores of such tropical countries as West Africa, for 

 these roots occupy and gradually fix the shifting mud- 

 banks. The roots are much branched, and thus intercept 

 all the silt and floating debris which collect about them. 

 Eventually the accumulations result in the formation of 

 new land, sometimes of great extent; for as soon as the 

 mud, etc., has raised the soil above the level of high tide, 



