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POPULAR HISTORY OF LICHENS. 



gated. They acquire a beautiful blue colour under the action 

 of iodine, and, when empty, they become variously bent and 

 twisted. The spores are the largest to be found in British 

 Lichens ; when isolated on a slip of glass they may almost 

 be distinguished by the naked eye. They are ellipsoid or 

 oval, elongate, unilocular, thick-walled. The epispore is very 

 thick, especially towards its extremities, where it gives way 

 during germination, allowing the protrusion of the bulging 

 endospore ; it is transparent, and consists of several layers 

 of unequal thickness and density. It is moreover coated ex- 

 ternally with a thick envelope of granular mucilage, which 

 frequently gives it a roughened appearance ; and this coat- 

 ing is apt to be mistaken for a true episporic layer. The 

 endospore contains a quantity of granular matter of a yel- 

 lowish or greenish tint, mixed frequently with large and nu- 

 merous oil-globules. Between the epispore and endospore 

 there is a considerable hyaline margin. The paraphyses are 

 linear and of great length ; along with the thecae they are 

 embedded in an abundant mucilage which swells greatly in 

 water. The spermogones are difficult of discovery, and oc- 

 cur as scattered, minute, black punctuations ; they are im- 

 mersed, have a simple, narrow, sinuous cavity, and a pale- 

 coloured envelope, which cannot readily be distinguished 



