44 LINDSAY, ON ABROTHALLUS. 



hood of Portree^ Skye, I fovmd the young apothecia indis- 

 tinguishable^ by the naked eye, from those of A. oxysporus. 

 These apothecia were flattened and black, with rough or 

 pulverulent surface, agglutinated borders, and surrounding 

 radiate-fissuring of the cortical layer of the thallus. The 

 adhesion of the margins of the apothecia to the cortical layer 

 is sometimes so intimate, that the base appears gradually 

 shaded off or passing into the matrix, like the perithecia of 

 Verrucaria epidermidis . This, however, is rare. I have seen 

 it only in a few hill specimens. The gradual contraction of 

 the hypothecium, or base of adhesion, renders the enucleation 

 of the old apothecia easy. 



Of the mode of evolution of the apothecia in his three 

 species, Tulasne says that^ in A. Smithii, " E matrice lente 

 ac tali modo emergunt ut ejus cutem \ix effringere illique e 

 'contrario primum marginibus adglutinari videantur;" in 

 A. Welivitzschii, " Matricis cuticulam ita in erumpendo 

 effringant ut istius frustula erecta hymenii discura quasi 

 vallo ambiant;" while, in A. microspermus , "E mati'ice pcde- 

 tentim emergit, cujus cuticulam fractam non sublevat et 

 isti e contrario toto anibitu adnasci s. conglutinari diu 

 videtur.^' The relations of the spothecial margins to the 

 surrounding cortical tissue do not appear to me to furnish 

 good characters for differentiation. I think I have seen all 

 the appearances which Tulasne describes in different speci- 

 mens of the varieties which I have designated ater and 

 pvlveruhntus , even from the same locality. The A. 

 Welw'itzsclvii of Leighton's ' Lich. Brit, exsicc' does not 

 differ, either in external characters or in internal structure, 

 from gTcen-pulveriilent forms of A. SmWiii found by myself 

 abundantly on Craigie Hill and elscAvhere ; but it rises 

 directly fi'om the ordinary thallus of Sticta fuHf/mosa. The 

 only specimen which I have had an opportunity of examining 

 has only two apothecia. One of these is flattened, not very 

 prominent, and appears agglutinated at the margins; the 

 other, on being moistened, becomes globose and substipitate, 

 and has distinctly no raised margin of cortical tissue. 

 Neither docs the degree of flattening or convexity of the 

 apothecia afford a good means of differential diagnosis; it 

 differs Avidely in specimens from various localities. The 

 apothecia of A. Smithii, says Tulasne, are "discoidea, 

 pulviniformia, tandemque maxime convexa;" those of A. 

 Welwitzschii are " magis vulgo deplanata ;" Avhile A. micro- 

 spermus, " attamen puncta atra latioi-a et depressiora iiilgo 

 sistit." I have frequently met with the apothecia both of 

 varieties « and /i flattened, sometimes tuberculiform and even 



