THE 



BRITISH SPECIES 



OF 



ANGIOCARPOUS LICHENS 



INTRODUCTION. 



Every botanist is fully aware how valuable and avail- 

 able a character is afforded by the form and external 

 markings of the seeds in very many species of Pha^no- 

 gamous plants ; the correct determination of the species 

 frequently depending exclusively thereupon. Analogous 

 reasoning leads us to the conclusion, that the form and 

 septa of the sporidia in Cryptogamic plants would present 

 similarly useful characters. Investigation proves the 

 correctness of this conclusion. Owing, however, to the 

 minuteness of the parts, the delicacy and care required in 

 the manipulation, and the employment of high magnify- 

 ing powers, these organs, in the family of the Lichens at 

 least, do not seem to have hitherto received that attention 

 which their importance really demands. This field of 

 research, fertile though it actually is, may therefore be 

 said to be comparatively a new and untrodden one, more 

 especially as regards British Lichens. Lichenists have 

 been, indeed, long aware of the existence and general 

 conformation of these particular organs, but it is believed 

 have never applied them to characterise or determine 

 species. 



Acharius, in his ' Lichenographia UniversaHs' (1810), 

 frequently mentions the asci and sporidia under the 

 names of cellulse and vesiculae, but neither searches into 



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