88 BERNT LYNGE. M.-N. Kl. 



Isidia distinctly corticate, sometimes their cortical hyphae grow out to short 

 hair-like, uncoloured emergences (water absorption?). Gonidia crowded, at 

 the central, inner part of the laciniae arranged in their normal position under 

 the upper cortex, at the free, ascending apical part quite as much within the 

 lower cortex Medulla white, with narrow, densely interlaced, occasionally 

 even apparently plectenchymatous h3'phae, gradually transformed into the 

 lower cortex, which is but slightly different from the medulla. Rhizinae 

 80 — 90 u thick, uncoloured or pale greyish. 



Apothecia and fertile pycnides not seen in Norwegian plants; Harmand 

 gives the size of the spores at 16,5 — 27 X 7'5~io ,"> accordingly a little 

 longer than in Ph. litliotra (Harmand 21—24 X 12 //, in this paper: 



15,7—22 (24) X 7-4— II' 13))- 



React. Cortex as well as medulla uncoloured by KOH as well as 

 b}' CaCloOo. (According to Har.mand: »Hymenium J -|- bleue persistant«). 



Hab. and loc. This species is certainly rare in Norway, though 

 probably overlooked on account of the minute and only slightly conspi- 

 cuous thallus. Only recorded on sunny, dry, chalky rocks at Leangen in 

 Asker near Kristiania (Lynge), associated with Flu virella and Ph. lithotea 

 and at Granvin in Hardanger on the cortex of Sorbus Aiicuparia (Lynge). 

 There were no transitional states between Ph. lithotea and Ph. scia- 

 strella. — In southern countries chiefly on bark. It is a well known fact 

 that towards their northern limit of distribution several corticolous Lichens 

 are also or exclusively found on rocks ■'^. 



The laciniae are so narrow that they might as well be called ramose 

 as incise. On account of the thin thallus, really good sections are not 

 easily obtainable. Thick sections are liable to give the investigator the 

 false impression of a plechtenchymatous medulla. 



The position of the gonidia is of a special interest. Their normal 

 place under the upper cortex is not of a fixed nature, if the (morphological I 

 lower side of erect laciniae offers sufficient opportunities for assimilation 

 the gonidia are also developed within the lower cortex. 



16. Physcia caesia (Hoffm.) Nyl. 



Lichen caesins Hoffmann Enumeratio Lichenum (1784) p. 65 et tab. XII, 

 fig. I (excellent). Acharius Prodromus (1798) p. 107. Wahlenberg Flora 

 Lappon. (1812) p. 422. 



1 Cfr. Edwin Nvl.^nder: Laf-vegetationen uti Savolax p. 62. 



