350 SYSTEMATIC 



more or less familiar home plants. Among the Pyrenocarpei, Verrucaria 

 (Pyrenuld) nitida occurs ; it is a widely distributed tree-lichen. 



It is unnecessary to describe in detail the British lichens. Some districts 

 have been thoroughly worked, others have barely been touched. The flora 

 as a whole is of a western European type showing the influence of the Gulf 

 Stream, though there is also a representative boreal growth on the moorlands 

 and higher hills, especially in Scotland. Such species as Parmelia pubescens, 

 P, stygia and P. alpicola recall the Arctic Circle while Alectoriae, Cetrariae 

 and Gyrophorae represent affinity with the colder temperate zone. 



In the southern counties such species as Sticta aurata, S. damaecornis, 

 Pliaeographis Lyellii and Lecanora (Lecania) hohphaea belong to the flora 

 of the Atlantic seaboard, while in S.W. Ireland the tropical genera Lepto- 

 gidium and Anlhracothecium are each represented by a single species. The 

 tropical or subtropical genus Coenogonium occurs in Great Britain and in 

 Germany, with one sterile species, C. ebeneum. Enterographa crassa is 

 another of our common western lichens which however has travelled east- 

 wards as far as Wiesbaden. Roccella is essentially a maritime genus of 

 warm climates : two species, R.fucifonnisund R.fucoides, grow on our south 

 and west coasts. The famous R. tinctoria is a Mediterranean plant, though 

 it is recorded also from a number of localities outside that region and has 

 been collected in Australia. 



In the temperate zones of the southern hemisphere are situated the great 

 narrowing projections of South Africa and South America with Australia and 

 New Zealand. As we have seen, the Antarctic flora prevails more or less in 

 the extreme southern part of America, and the similarity between the lichens 

 of that country and those of New Zealand is very striking, especially in the 

 fruticulose forms. There is a very abundant flora in the New Zealand 

 islands with their cool moist climate and high mountains. Churchill 

 Babington 1 described the collections made by Hooker. Stirton 2 added 

 many species, among others Calycidium cuneatum, evidently endemic. Later, 

 Nylander 3 published the species already known, and Hellbom 4 followed 

 with an account of New Zealand lichens based on Berggsen's collections ; 

 many more must be still undiscovered. Especially noticeable as compared 

 with the north, are the numbers of Stictaceae which reach their highest 

 development of species and individuals in Australasia. They are as numerous 

 and as prominent as are Gyrophoraceae in the north. A genus of Parmelia- 

 ceae, Hetorodea, which, like the Sttctae, bears cyphellae on the lower surface, 

 is peculiar to Australia. 



A warm current from the tropical Pacific Ocean passes southwards along 

 the East Coast of Australia, and Wilson 6 has traced its influence on the 



1 Babington 1855. a Stirton 1875. 8 Nylander 1888. 4 Hellbom 1896. 



6 W41son 1892. 



