1916. No. 8. MONOGRAPH OF THE NORWEGIAN PHYSCIACEAE. 77 



1369 (s. n. Panmlia obscitra var. lithotea Ach.). Migula Krypt. Germ. 

 931 (f sciastra s. n. Physcia obsaira (Ehrh.) Xyl. f. orbicularis (Neck.I 

 Th. Fr.). Xorrl. et Xyl Herb. Lieh. Fenn. 220 (f. sciastra, s. n. Ph. 

 lithotea (Ach.) Xyl). 



Thailus small or middle-sized, orbicular, 2 — 4 cm. in diam,, but incli- 

 ned to gro\y in dense clusters, covering larger areas; on plane substratum 

 closely appressed, on uneven (e. g. moss) at the circumference more or 

 less free from the substratum or even slightly ascendant. Laciniae stel- 

 late, elongate, narrow: 0,2—0,5, rarely up to 0,8 — i mm. broad, 

 close!}- contiguous or imbricate, towards the centre alwavs imbricate. 

 Laciniae very multifid, either pinnato-incise or furcate, with acute angles; 

 long branches with straight or slight!}' undulate outlines, subascendant 

 laciniae usually shorter and broader with more or less undulate margin. 

 Thallus without soredia, but at the margin of the laciniae 

 and at the ends of the short lateral branches are formed 

 short furfuraceous or more elongate, branched isidia. Towards 

 the centre the isidia frequently spread over the whole thallus and become 

 confluent. Thalli without isidia are occasionally found (young thai!!?). 

 If the cortex of the isidia is broken off, the}' occasionally develop soredia- 

 like forms (isidia sorediose fatiscentia) Thallus fragile, opaque, epruinose, 

 laciniae plane or sometimes with slightly ascendant margin. The colour 

 varies from grey or pale greyish-brown through greyish- 

 black to black, lower side always black, even on ascendant laci- 

 niae. Laciniae with long pale cilia or rhizinae at the margin, the rhizinae 

 of the lower side are black, only slightly visible — owing to the closely 

 contiguous laciniae — , very branched, thick: to 120« at their base. 



Thallus covered with a thin, amorphous, finally insperse stratum, 

 upper cortex at the exterior part more or less dark greyish-brown, other- 

 wise uncoloured. Hyphae perpendicular to the surface, thin-walled, con- 

 strictedly septate with rounded articuli. Isidia distinctly corticate. Upper 

 cortex of an irregular thickness (to 25 a), on account of the uneven sur- 

 face of the gonidia, gonidia also occasionally filling out the whole thin 

 white medulla. Thallus thin, rarely more than 200 u thick. 



Thallus usually fertile; apothecia sessile to closely appressed, middle- 

 sized. I, rarely 2 or 2,5 mm. in diam. Margin persistent, entire or cre- 

 nate, sometimes shortly appendiculate. Receptacle black around the centre, 

 uncoloured towards the margin, with scattered black rhiziniae on the lower side. 

 The hyphae of the cortex perpendicular to the surface, middle thick-walled, 

 constricted!}' septate with rounded articuli. Gonidia crowded within the unco- 



