107 



NEW RARE OR CRITICAL LICHENS, 

 By W. Watsoi^, B.Sc. 



The possibility of obtaining dyes from licbens has aroused a 

 greater interest in these plants than has been shown for many years, 

 and the difficulty of obtaining sufficient dyes by other methods may 

 render the process of obtaining dyes from lichens economically possible. 

 The "crottle" and the " lit-pig," the adjuncts to this home-industry 

 of the crofters, have never been entirely abandoned in the Scottish 

 Highlands, and may again come into favour. Considering the 

 increase of interest in these plants and the slight amount of attention 

 paid to them in recent years, there need be no apology for the follow- 

 ing notes, but an apology may be necessary for the description of new 

 species, since these chiefly depend on microscopic characters and add 

 further species to genera which are alread}^ overburdened. No other 

 course, however, seems to be available, unless one is bold enough to 

 "lump" many of the so-called species together, and place the '* small 

 species " as varieties. The evidence is not sufficient to warrant this 

 course, and other lichenologists who have seen the specimens consider 

 it advisable to publish them as new. The difficulties of correlation 

 between British and Continental lichenological works are dealt with 

 in some of tlie notes concerning some of our common species. 



The numbers following the localities are those of the vice-counties. 



Thelidium terrestre, 



vel leprosus, viridis vel 



sp. nov. Thallus tenuis, crustaceo-effusus 

 viridi-nigrescens, hyphis paucis, gonidiis 

 viridibus. Perithecia minuta, nigra, 

 sparsa, semi - immersa tandem 

 emerso-sessiiia, dimidiata ; tunica 

 externe nigro - brunnea, interne 

 cinereo-brunnea; ostiolo minuto 

 baud depresso ; h^^nenio sine 

 gonidiis ; aseis clavatis ; para- 

 physibus hyalinis evanescentibus 

 vel null is ; osteolis filamentis aut 

 paucis aut nuUis ; gelatina hy- 

 menia Isete rubra cum iodo ; 

 sporis octonis, hyalinis vel albido- 

 cinereis, ellipsoideis, granulis, ab 

 altera parte plerumque angustati- 

 oribus, uniseptatis, 0-016-28 mm. 



^o^ . . .v^ . . longis, 0007-11 mm. latis, in 



^j Y I ) \S| ) — \ medio leviter constrictis. Ad 



terram. ' 



Thallus thin, crustaceo-efifuse 

 or leprose, green or darker, with 

 green algal cells (Pleurococcus) 

 and few hyphje. Perithecia 

 minute, black, scattered, semi- 

 immersed, at length more or less ssssile, dimidiate ; outer wali 

 dark brown, inner paler- brown ; minute ostiole not depressea ; 



i2 



A. Polyblastia mortensis. Ascus X 125 ; 



three spores X 500. 



B. Thelidium terrestre, Perithecium X 25 ; 



ascus X 125 ; two spores X 500. 



