74 BERNT LYNGE. M.-N. Kl. 



Thallus usually covered by an amorphous uncoloured stratum. Upper 

 cortex up to 40 u thick, cortical hyphae distinct, perpendicular to the 

 surface, constrictedly septate, thin-walled with great lumina. Gonidia 

 arranged in a thick irregular, continuous stratum under, occasionally in the 

 cortex. Medulla white. Lower cortex black, 25 50 /< thick. 



Most frequently sterile, but fertile plants are not rare. Apothecia 

 orbicular, small, diam. i 1,5( 2) mm., sessile, loosely affixed Margin 

 prominent, thick, persistent, entire or crenate, esorediate. Receptacle 

 even or minutely rugose, black around the centre, of the same colour as the 

 thallus towards the circumference, usually without, but occasionally with 

 rhizinae. Cortex 25 50 /< thick, its hyphae perpendicular to the surface, 

 thickwalled, constrictedly septate. Gonidia in dense clusters in the margin, 

 and scattered in the whole medulla, especially within the uncoloured parts 

 of the cortex and under the hypothecium, few or entirely absent within 

 the black cortex. Hypothecium up to 55 , thick, almost uncoloured, formed 

 of thick-walled densely interlaced plectenchymatous hyphae, arranged 

 tangentially to the hymenium. Disc reddish-brown, plane, epruinose. 

 Hymenium covered with an uncoloured amorphous stratum, which occa- 

 sionally breaks up into an insperse mass. Hymenium to 105 ^i thick, 

 yellowish- brown at the exterior part, otherwise uncoloured and not insperse. 

 Paraphyses at their tips clavately incrassate, distinctly constrictedly septate, 

 occasionally with some short branches Asci 52 65 t long, 1318 it 

 thick, octosporous. Spores obliquely biseriate, straight, typically ellipsoidal: 

 not constricted at the septum, rounded at their apices and at least twice 

 as long as they are thick. Colour greyish-brown, old spores almost 

 opaque. Spores with distinct pore canal, septum thick, cell rooms angular, 

 stretched across of the spores, or rounded like a sand-glass. Size 

 (14 )i7 25 u long, (7 )8 12 t u thick. 



Pycnides frequent, but rapidly destroyed by the expanding soredia. They 

 protrude slightly at the ostiolum, and are subglobose, diam. 160 

 240/4. Perifulcrium brownish around the ostiolum, otherwise qncoloured. 

 Pycnides straight, broadly fusiform or subelliptical, 2 4/4 long, i 2/t thick. 



React. Neither cortex nor medulla coloured by KOH or CaCloCX. 

 Hymenium first blue, then at once vinous red by J. 



Hab. On the trunks of deciduous trees (not on Betttla], and on 

 moist rocks, especially schistose and calcareous. North of Salten only 

 recorded on chalk. 



Loc. Physcia virella is a lowland species, frequent or even abundant 

 at least as far north as Trondhjem, probably with the exception of our 



