66 BERNT LYNGE. M.-N. Kl. 



ning along the sides of the laciniae, in central laciniae also at their 

 apices, and sometimes covering the whole surface. Thallus (with us only 

 slightly) pruinose at the apices of the laciniae, pruina whitish or pale 

 bluish. Colour chest-nut brown or cervine, sometimes with a tinge 

 of grey, soredia white or yellowish. Lower side black, rhizinae black 

 (only young rhizinae along the circumference are pale), from undivided to 

 much branched. 



Thallus covered with a thin amorphous stratum. Upper cortex with 

 an exterior, brownish or yellowish-brown, equally thick (14 16/<) part, 

 a thicker interior part is uncoloured. The thickness of the cortex is very 

 variable, from o (soredia) to 80 /<. Its hyphae 4 5 u thick, septate, but 

 only slightly constricted; at the interior part of the cortex they spread 

 irregularly, at the exterior part they are perpendicular to the surface. 

 Gonidia glomerate, of a very variable distance from the surface. Medulla 

 white, lower cortex black, up to 50 t u thick. 



Apothecia not seen in Norwegian specimens 1 . Pycnides not rare, 

 globose or somewhat prominent at the ostiolum, diam. 130 i6o/<. Peri- 

 fulcrium dark around the ostiolum, otherwise uncoloured. Pycnoconidia 

 straight, cylindrical, 3 4 (.t long. 



React. When yellowish, the soredia are coloured more distinctly 

 yellow by KOH. - 



The var. detersa is rare in Norway, and is only known from our Cen- 

 tral Lowlands: Ringebu (hb. SOMMERFELT s. n. venusta /? hybrida ACH., 

 pulverulenta var. hybrida SOMMERFELT*), Norderhov (hb. NORMAN), and 

 from Minne, near the railway bridge, at Betula (LYNGE). 



HUE considers var. leucoleiptes TUCK, and var. detersa NYL. as syno- 

 nymous plants. NYLANDER'S plant in Herb. Lich. Fenn. No. 213 is almost 

 epruinose with narrow pinnato-multifid laciniae, whereas TUCKERMAN'S 

 plant in Lich. Amer. sept. No. 107 has coarser and very pruinose laciniae. 

 The habitus is different, but these characters are variable in Physcia, and 

 it is probable that HUE is right. MERRILL'S plant in Lich. Exs. No. 118 

 is more like our Norwegian ones. 



In any case the Norwegian plants can with certainty be referred to 

 var. detersa NYL. (Herb. Lich. Fenn. No. 213). 



Great importance has been attributed to the colour of the lower side. 

 HUE and after him HARMAND are of opinion that a black lower side is a 



1 According to NYLANDER Synopsis p. 420 the spores are large: 27 44X14 2O//. 



