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POPULAR HISTORY OF LICHENS. 



glomerate thallus, or to be formed of a series of super- 

 imposed, but confused, layers of thalline tissue. Many of 

 the specimens are irregularly fissured on the surface, the 

 fissures apparently passing into an obsolete central cavity, 

 which has probably been the base of attachment of the plant 

 to the twigs of trees. This attachment has probably been 

 very loose ; the Lichen has been detached by the wind, and 

 from rolling along the surface of the ground, from a peculiar 

 curling in or involution of the foliaceous thallus, as well as 

 from repeated growths of secondary thalli upon the parent 

 thallus, the present form has been apparently produced. It 

 is contrary to all analogy to suppose that this Lichen has 

 been free or non-adherent from birth ; at the same time it 

 is evident that it has grown and increased in size subsequent 

 to the period of its detachment from its base of support. 

 While this is a rare instance of a plant growing vigorously 

 after all connection with its base of support has been severed, 

 it illustrates, in a most conclusive manner, the fact that the 

 nutrition of Lichens is often wholly independent of soil, and 

 it also exhibits the influence of epithalline growths, of the 

 multiplication of secondary thalli, in modifying the form of 

 Lichens. It would appear however that we are not rigidly 

 bound down to the necessity of believing that this Lichen 



