CHAP. IV. 



FUNCTION OF NUTRITION. 



237 



of a trailing plant (Cissus angustifolia). In our own 

 country the genera Orobanche, Cuscuta, Lathraea, Mono- 



tropa, and Epipactis afford us leafless parasitic species. 

 These do not appear to be very injurious to any woody 

 plants which they attack; but such as grow on herba- 

 ceous species are highly mischievous. The species of 

 " Cuscuta" are among the most curious of this kind. 

 When they first germinate they have a stem formed 

 like a delicate thread, which is leafless and soon coils 

 itself round the stem of some plant growing in the 

 neighbourhood. To this it adheres by means of suck- 

 ers formed of wart-like protuberances at intervals along 

 its stem. When it has obtained firm hold of the plant 

 round which it has coiled, its root decays and the 

 stem ceases to have any connection with the soil, but 

 vegetates and produces flowers at the expense of the 

 proper juices of the plant to which it is attached. The 

 common misseltoe and other Loranthese being furnished 

 with green leaves are able to elaborate crude sap into 

 proper juice ; but as they are destitute of any true 

 root they possess the property of penetrating through' 

 the bark of the trees to which they are attached, and 

 of fixing the base of their stems into the wood be- 

 neath. Thus they absorb the rising sap in its progress 

 towards the leaf. It is asserted that a branch of mis- 

 seltoe when placed in water has|po power of absorbing 

 this fluid, but that when the branch to which it is still 



