CRYPTOGAM! A ALGJE. 859 



if it had been rin;7,ed or fcorcheJ by fire-, tl/e 

 grey colour of t!ie bliners being derived fror.i 

 innumerable minute InMrv grains, with which 

 they are covered, and wJiich give them a kind 

 of chagreen afperity. The margin of the leaf 

 in particular, and a confiderable portion of the 

 more interior part of it, is covered with a black, 

 footy furfural eous fiibltancc, which, by ihc aid 

 pf a microlcopc, appeais to conful of numerous 

 branched pedicles, grov.'ing in clullcrs, fome- 

 whst fimil.ir to thofe already ucfcribed on the L- 

 gl omul if eras, but much fiiorter and imaller, and 

 of a footy colour. No otiicr fruclifications have 

 ever yet been dilcovered. 



Tne under fide of the leaf is of a dufky grey or 

 bhckifli colour, fmooth, and without radicles, 

 but full of pits or cavities, correfoonding fo tlie 

 bliilers en the upper fide. Tiie only root by 

 which the plant adheres 10 the rocks is placed in 

 the centre of the leaf, as is ufual in the fpecies 

 of this divifion. 



When the plants grow old, they fomctimes extend 

 themlelves to the breadtii of four or five inchc^ 

 and are divided into deep unequal fegmcnts, as 

 Micheli has figured it in the place above quoted, 

 and BiUenius in his Hijl, mule. t. 30. /. 13 f. A. 



When the plant i^ wet it turns to a dull fufcous 

 green colour. 



iv. uni- 



