CONFERVA DECORTICANS. 



C. filamentis fimplicibus, tenuifTimus, denfiffime contextis, cocruleo- 

 viridefcemibus ; diffepimeniis obfcuris ; articulis brevibus. 



On damp walls and ftones not uncommon. 



THIS fpecies, which appears hitherto to have efcaped obfervation, is by no 

 means unfrequent on walls and (tones much expofed to moiflure. I firft 

 detected it mixed with C. muralis, on the pump facing Stationer's Hall, 

 in London, and fince in firnilar fituations in feveral of the Weftern counties. It 

 grows in large glaucous patches, fo intimately woven as to peel off in flakes, 

 bearing a confiderable refemblance to a piece of filk or ribbon : its filaments, 

 which it is impoffible to difentangle fo as to afcertain their length, are extremely 

 flender, of a deep glaucous color, and fome of them are very (lender : diflepiments 

 xnay be obferved regularly difpofed at diftances about equal to the thieknefs of 

 the filament. 



From C. muralis it differs in its much greater tenacity, and darker color j 

 from C. limofa in the former, and its far different mode of growth -, and from 

 both thefe, and indeed all others, it may be diftinguifhed by its forming patches 

 fo denfely matted as to peel off in thin ftrata, as is above defcribed. 



The furface is in general very fmooth and glofly; but when the wall on which 

 it grows is occafionally wafhed by a ftronger dream of water than ufual, as 

 frequently happens at mills, its filaments are lengthened out, and the furface 

 afiumes a more fhaggy appearance. 



In drying, it does not appear to fuffer any change, and adheres to both glafs 

 and paper. 



A. C. decorticans, natural Cze. 



B. Ditto, magnified, i. 



