LICHENES 343 



immersed in the bark, or the numerous species present on 

 persistent, coriaceous leaves in the tropics, are more or 

 less parasitic is yet an unsettled question. Apart from 

 this, it is known that lichens are often injurious to trees 

 when present on the trunk and branches in quantity, and 

 this is more especially the case with nursery stock. 



It has been shown by Waite that spraying with Bordeaux 

 mixture of full strength kills the lichens present on pear 

 trees. This method would, as a matter of course, prove 

 equally effective in the case of other kinds of trees. 



Finely powdered lime sprinkled on the branches during 

 daiTip weather is also said to remove lichens. 



Cephaleurus mycoidea, Karsten = Cephaleu7-us virescens, 

 Kiinze; Mycoidea parasitica, Cunningham. — This lichen 

 is abundant on the polished, coriaceous leaves of many 

 kinds of plants in tropical regions ; among genera of 

 economic importance may be mentioned Coffea, Citius, 

 Camellia, Anona, Cinnamomum, and Quassia. Dr. Watt 

 states that in Assam it may be said to occur on any tree 

 or bush the leaves of which have, like the tea plant, a fairly 

 hard and polished epidermis on the upper surface. 



On leaves the plant first appears as circular orange 

 patches ; at a later stage the patches change to green, 

 or greyish-green, finally becoming white and polished 

 like porcelain, and are circular or irregularly branched. 

 Minute black spots are usually present on the white 

 patches, corresponding to the ascigerous form of the 

 fungus. 



So far as the tea plant is concerned, it appears that so 

 long as the disease is confined to the leaves but little 

 injury results, whereas, according to Cunningham, when it 



