96 LICHENACEI. [CAUCIUM. 



Hob. On old pales in upland tracts. Distr. Only sparingly in S. 

 England. B. M. : Wheatfield Park, Oxfordshire. 



14. C. populneum De Brond. in Dub. Bot. Gall. (1830) ii. 

 p. 638. Thallus hypophlseodal, macular, subleprose, pale or whitish. 

 Apothecia minute, scattered, entirely black, somewhat shining ; 

 stipes very short, slender ; capitulum turbinate ; spores 1-septate, 

 blackish, 0,010-11 mm. long, 0,005-6 mm. thick. Mudd, Man. 

 p. 257, t. iv. f. 104; Leight. Lich. Fl. p. 45, ed. 3, p. 44; 

 Cromb. Grevillea, xv. p. 14. Calicium curium /3. populinum Turn. 

 & Borr. Lich. Br. p. 149; Sm. Eng. Fl. v. p. 140. Calicium 

 triste Cromb. Lich. Brit. p. 13. 



The thallus is somewhat smooth and shining, appearing as a very thin 

 film. From C. parietinum, which it somewhat resembles, distinguished 

 by its place of growth, the minute, fragile apothecia and the' larger 

 spores. 



Hab, On the smooth bark of poplars in wooded upland tracts. Distr. 

 Only sparingly from the S.W. Highlands of Scotland and S.W. Ireland. 

 B. M. : Airds, Appin, Argyleshire. Killarney, co. Kerry. 



15. C. diploellum Nyl. Flora, 1868, p. 161. Thallus effuse, 

 very thin, greyish-white, but doubtfully proper. Apothecia minute, 

 scattered, entirely black; stipes very short; capitulum turbinate, 

 open : sporal mass scarcely prominent ; spores simple or at length 

 1-septate 0,006-9 mm. long, 0,003-4 mm. thick. Carroll, Journ. 

 Bot. 1868, p. 100; Cromb. Lich. Brit. p. 13; Leight. Lich. Fl. 

 p. 39, ed. 3, p. 39. 



Apart from other marks of distinction, this may be recognized by its 

 very small size, being the most minute of all Caliciei, so that it is very 

 liable to be overlooked. It is closely allied to C. disseminatum, a European 

 species, which has not yet been detected in Great Britain, 



Hob, On the bark of holly in upland wooded districts. Distr. Ex- 

 tremely local and scarce, in 'S.W. Ireland. B. M. : Cromaglown, Kil- 

 larney, co. Kerry. 



16. C. retinens Nyl. Flora, 1868, p. 161. Thallus effuse, thin, 

 subfarinaceous, opaque, whitish. Apothecia minute, sessile, leci- 

 deiform, black ; sporal mass indistinct ; spores oblong or oblongo- 

 cylindrical, conspicuously 1-septate, 0,008-11 mm. long, 0,0025- 

 35 mm. thick; hypothecium brownish-rubricose. Leight. Ann. 

 Mag. Nat. Hist. ser. 4, i. p. 482; Lich. Fl. p. 45, ed. 3, p. 44; 

 Cromb. Grevillea, xv. p. 14. 



It is doubtful if the thallus be really proper. This may be decided 

 by additional specimens. With its lecideiform apothecia and indistinct 

 mazaidium and definitely 1-septate spores it seems referable to Trachylia; 

 but it rather presents, according to Nylander, in lift., an affinity with 

 species of the present genus, especially in the longer spores. At the 

 same time it shows that there are no decided limits for the two genera. 



Hab. On the trunk of an old oak in a maritime district. Distr. Met 

 with only once, and very sparingly, in the Channel Islands, on the coast 

 of Jersey. 



