388 ECOLOGY 



a height of 3861 m. he collected four mosses and sixteen lichens. These 

 were : 



Stereocaulon condensatum. Candelaria concolor. Buellia discolor. 



Gyrophora cylindrica Caloplaca pyraceavsx . nivalis. Buellia stellulata. 



Gyrophora spodochroa. Haematomma ventosum. Lecidea contigua var. steriza 



Solorina crocea. Acarospora smaragdula. Lecidea confluens. 



Solorina saccata. Psora decipiens. Dermatocarpon hepaticum. 

 Parmelia encausta. 



He found that as he climbed higher and higher foliaceous species became 

 rarer and crustaceous more abundant. The colour of the lichens on the high 

 summits was slightly weakened and the thallus often reduced, but all were 

 fertile and the apothecia normal and sporiferous. Lichens at less high 

 altitudes where they emerge from the snow covering for longer periods and 

 enjoy light and sunshine are, as already observed, often very brightly 

 coloured and of luxuriant growth. 



d. Tundra Lichens. In phyto-geography the term "tundra" is given 

 to great stretches of country practically treeless and unsheltered within the 

 Polar climate ; the tundra extends from the zone of dwarfed trees on to the 

 permanent ice or snow fields. The vegetation includes a few dwarfed trees, 

 shrubs, etc., but is mainly composed of mosses and lichens ; the latter being 

 the most abundant. These are true climatic lichen formations. 



Leighton^ in describing lichens from Arctic America brought home by 

 the traveller, Sir John Richardson, quotes from the latter that : " the ter- 

 restrial lichens were gathered on Great Bear, and Great Slave Lakes before 

 starting on our summer voyages after the snow had melted.... The barren 

 grounds are densely covered for many hundreds of miles with Corniculariae 

 and Cetrariae, and where the ground is moist with Cladoniae, while the 

 boulders thickly scattered over the surface are clothed with Gyrophorae.... 

 The smaller stones on the gravelly ridges of the Barren Grounds are 

 covered with lichens." 



The accounts of tundra lichens that have been given by various travellers 

 deal chiefly with the more prominent terricolous forms. They have been 

 classified as " Cladina tundra," including Cladonia rangiferina and Sphaero- 

 phorus coralloides, " Cetraria tundra," and " Alectoria heath," the latter the 

 hardiest of all. Great swards of these lichens often alternate with naked 

 stony soil. 



Kihlman^ has noted, as characteristic of tundra formations, the compact 

 cushion-like growth of the mosses which are thus enabled to store up water 

 and to conduct it by capillarity throughout the mass to the highest stalks. 

 Certain tundra lichens take on the same growth character as adaptations to 

 the strenuous life conditions. Cetraria glauca i. spadicea with i. congesta and 



^ Leighton 1867. 2 Kihlman i8go. 



