28 BERNT LYNGE. M.-N. Kl. 



var. tenera, (HAVAAS) LYNGE. 



Physcia tenera HAVAAS Lich. Norv. exsic. 425. 



Tab. Ill fig. 2. 



Thallus small, orbicular, 2 3 cm. in diam Laciniae closely appressed 

 to the substratum, multifid, repeatedly divaricately furcate or pinnate, 

 with acute angles, discrete, continuous from the centre to the circum- 

 ference, linear, eaqually broad, very narrow: 0,3 0,5 mm. broad, with 

 undulate contours. Thallus epruinose, without isidia or soredia, colour 

 pale greyish-white, lower side uncoloured. Thallus resting on a cushion 

 of well developed, branched rhizinae on the lower side and at the margin 

 of the laciniae. Rhizinae grey or somewhat darker towards the centre. 

 Secondary laciniae not seen. 



Thallus very thin (100 /(). Upper cortex 2025 /' thick, its hyphae 

 adsperse and very indistinct, discernable only in very thin sections, per- 

 pendicular to the surface, constrictedly septate with rounded articuli. Goni- 

 dia numerous, arranged in a thick stratum, filling tip the greater part of 

 the medulla. Medullary hyphae very loosely interlaced, no distinct limit 

 between the medulla and the lower cortex. Hyphae of the lower cortex 

 very thick-walled, densely interlaced, refractive, more or less parallel to the 

 surface, uncoloured. Lower cortex 20 30 ju thick. 



Apothecia numerous, orbicular, small, 1 1,5 mm. m diam., sessile, 

 but not appressed, disc epruinose, margin persistent, very thin, minutely 

 crenate. Spores rather small: 16,3 19,8/4 long, 7,9 9,2 // thick. The 

 texture of the apothecia otherwise entirely as in the species. 



Reaction as in the species. 



Hab. On the smooth bark of Populus tremula, far from the ground, 

 in subalpine stations (300 350 m. s. m.). 



Loc. Only recorded from Granvin in Hardanger, Western Norway 

 (HAVAAS). 



I am unable to regard this plant as a proper species. It grows asso- 

 ciated with forms of Ph. aipolia which have also very narrow laciniae, 

 (convergent forms). Its very local distribution indicates a modification of 

 the habitat. 



2. Physcia aipolia (ACH.) NYL. 



Lichen aipolius ACHARIUS Prodromus (1798) p. 112. 



Parmelia aipolia ACHARIUS Methodus (1803) p. 209, ACHARIUS Lich. 



