ROBBERY AND MURDER, 241 



orders have adopted it. We cannot peruse any 

 work of travel in tropical regions, especially if the 

 writer knows anything of botany, without finding 

 references to and descriptions of beautiful epiphytal 

 Orchids. Growing attached to the trunks of trees, 

 in elevated situations, they are very conspicuous, and 

 as they have no huge stem to build up, we have 

 seen they devote their whole substance to the im- 

 portant act of flowering, the green stem and roots 

 being usually covered with stomata, for the perform- 

 ance of leaf-functions. 



But mere attachment to the bark of trees, like 

 that sought by our Ivy, may eventually result in the 

 adventitious roots (at first developed simply as 

 holdfasts) intercepting and obtaining some of the 

 sap of the tree. There are not wanting botanists 

 who hold that the Ivy occasionally indulges in this 

 habit. If this be true, then it furnishes us with an 

 illustration of an epiphyte being transformed into a 

 parasite. 



The type of vegetable parasite represented by the 

 common Mistletoe must have been practising the 

 habit for ages. This is indicated both by its root- 

 structure and its geographical distribution. Its 

 root-fibres obey quite a different law to that which 

 governs the early behaviour of the roots of other 

 plants. Whilst the latter grow downward, those of 

 the Mistletoe grow towards the centre of the branch 

 the plant is parasitic upon, and afterwards completely 



R 



