igi6. No. 8. MONOGRAPH OF THE NORWEGIAN PHYSC1ACEAE. 



Fig. 7. Physcia pulverulenta var. 

 ailochroa (Ehrh.) Th. Fr. 



very few under the hypothecium, scarcely scattered in the medulla. Disc 

 plane, whitish or bluish-white pruinose, or naked, black or dark brown. 

 Hypothecium pale yellov, up to 5060^ thick, plectenchymatous. Hyme- 

 nium covered by a densely inspersed, amorphous, uncoloured stratum. Hy- 

 menium at the exterior part brown or reddish-brown, otherwise uncoloured 

 and not inspersed, 130 230^ thick. Paraphyses separating easily, usually un- 

 divided, occasionally branched, near their apices indistinctly septate, equally 

 broad or slightly clavato-incrassato above (3 5 /t). Asci broadly clavate, 

 no 140 <u long, 26 35 1.1 broad, octosporous. Spores obliquely biseriate, 

 broadly rounded at their ends, 

 straight and only slightly constricted, 

 rarely slightly fabiform, in which case 

 a little more constricted at the septum. 

 Young spores have a small angular 

 lumen and a distinct pore-canal; during 

 maturation the lumen becomes more 

 rounded and the cell wall thinner. 

 Colour dark greyish-brown, at last the spore becomes almost black and 

 opaque. The breadth is always more than half the length, the size 24 36 u 

 long, 14,6 20,2 4 broad. 



Pycnides numerous, but easily overlooked, owing to the entirely unco- 

 loured perifulcrium. They are large: 240 320^ high and 240 250 u 

 broad. Pycnoconidia cylindrical, straight or slightly curved, 4 6 j.i long. 



Reaction: Cortex and medulla uncoloured by KOH as well as by 

 CaCl 2 O 2 . Hymenium first blue, then vinous by J. 



Hab. The var. ailochroa is distinctly a lowland species, not known higher 

 than 600 meters above sea level (Hoi), and very rare indeed at that 

 elevation. It requires air and light, and is found on the bark of large trees 

 in open situations (avenue-trees, isolated groups of Fraxinus, Populus, 

 Alnns, Acer, Tilia not on Betula). It is very rarely found on stone 

 (Moster, moist Atlantic climate). 



It is a species chiefly of south-eastern distribution. There is hardly 

 any Physcia more frequent about the Kristiania-fjord. It is much less fre- 

 quent along the southern and western coast and especially at the inland 

 end of the great western fjords. I have not seen quite typical states 

 north of Trondhjem (Drontheim). In Northern Norway it is replaced by 

 angustata-forms. 



Loc. Numerous habitats around Kristiania (M. N. BLYTT, N. LUND, 

 N. G. MOE), in old times also from the town itself, where the smoke has 



