426 ucn.EN'ACEi. [LECANORA. 



Form calcigena Nyl. ex Cromb. Journ. Bot. 1876, p. 361 

 (nomeu); Leight. Lich. Fl. ed. 3, p. 192. Thallus determinate, 

 thicker, areolato-diffract, greyish. Apothecia livid, subpruinose, the 

 thalline margin entire. 



Differs in the characters given of the tballtts and apothecia. It is 

 probably a good variety, but has been seen too sparingly to decide. 



Hab. On calcareous rocks in a maritime district. Distr. Very local 

 and scarce in N. W. Ireland. B. M. : Lettermore, Connemara, co. Galway. 



107. L. Agardhiana Ach. Syn. (1814) p. 152 ; Nyl. Lich. Scand. 

 p. 138. Thallus effuse, thin, contiguous, smooth, opaque, dark- 

 greyish (K , CaCl ). Apothecia small, at first innate, concave, 

 with whitish entire thalline margin, at length sessile, convex, im- 

 marginate, brownish-black, slightly pruinose or naked (epithecium 

 HNo 3 rosaceous) ; spores ellipsoid, 0,010-14 mm. long, 0,004-5 mm. 

 thick ; paraphyses thickish, brownish at the apices ; hymenial gela- 

 tine bluish with iodine. Cromb. Grevillea, xviii. p. 69. 



A plant, according to Nylander in lilt., allied to L. Hageni, though the 

 apothecia are at length lecideoid. In the few British specimens the 

 thallus is indistinct, so that they may be referred to a form ecntstacea 

 Cromb. The apothecia are numerous, though not crowded, and for the 

 most part epruinose. The spermogones are rarely present, with spermatia 

 0,012-15 mm. long, 0,0005 mm. thick. 



Hab. On calcareous rocks in a maritime district. Distr. As yet only 

 in N. Wales. B. M. : Great Orme's Head, Carnarvonshire. 



108. L. prosechoides Nyl. Flora, 1872, p. 250. Thallus deter- 

 minate, thinnish, areolate-rimose, whitish or sordid-yellowish (K , 

 CaCl ). Apothecia small or moderate, plane, somewhat prominent, 

 brownish or blackish, the thalline margin subentire ; spores 

 ellipsoid or oblongo-ellipsoid, occasionally 1- septate, 0,008-12 mm. 

 long, 0,0045-55 mm. thick ; paraphyses discrete, moderate or 

 thickish, brownish or yellowish-brown at the clavate apices ; hy- 

 menial gelatine persistently bluish with iodine. Cromb. Grevillea, 

 iii. p. 82. Lecanora umbrina subsp. prosectioides Nyl. in Cromb. 

 Lich. Brit. (1870), p. 51 ; forma proseclwides Leight. Lich. Fl. p. 208, 

 ed. 3, p. 191. To this fide Nyl. in litt. is referable Lecanora 

 helicopis f. dilutior Nyl. Lich. Scand. p. 159, Carroll, Journ. Bot. 

 1866, p. 23, Cromb. Lich. Brit. p. 50; also Parmelia subfusca var. 

 lainea Fr. Lich. Suec. Exs. n. 371. Lecanora prosecha (non Ach.) 

 Leight. Lich. Fl. ed. 3, p. 224. Brit. Exs. : Cromb. n. 67; Larb. 

 Lich. Hb. n. 94. 



At first regarded as a subspecies of L. umbrina by Nylander, this 

 differs in the colour of the thallus and of the apothecia, in the form of 

 the spores, and in the reaction of the hymenial gelatine. The thallus, 

 though determinate, is at times somewhat expanded, and varies in colour, 

 being paler in shady situations. The apothecia are numerous, with the 

 thalline margin occasionally at length obliterated. They are rarely the 



