lo DISCOVERY REPORTS 



Verrucaria tesselatula is a subantarctic-bicentric, or perhaps circumpolar, species with an extension 

 into the antarctic in the Graham Land sector. Staurothele gelida is also subantarctic-antarctic in its 

 distribution, but apparently confined to the South American sector. 



Consideration of these endemic antarctic and subantarctic species raises the question of vicarious 

 representation, which has been touched upon by Degelius in his studies of the relationships between 

 the lichen floras of Europe and North America (1940). He finds that in addition to vicarious species 

 which simply replace each other in the two areas under consideration, there is a second type, for which 

 he proposes the term ' subvicarious species', in which nearly related species almost, but not entirely, 

 replace each other in their distribution. It is interesting to find the same phenomenon among the lichens 

 of the northern and southern hemispheres. One of the best examples of such a subvicarious pair is 

 furnished by the two species oi Neuropogon, N. sulphureus and A'^. antarcticus (Lamb, 1939). The former 

 is the only representative of the genus in the Arctic ; the latter, very closely allied morphologically, 

 largely takes its place in both the Falklands sector and the Ross Sea area, but N. sulphureus is also 

 present, notably on the eastern side of the Graham Land peninsula. Instances of bipolar vicarious 

 and subvicarious species among the Pyrenocarp lichens can be tabulated as follows : 



Northern hemisphere Southern hemisphere 



Vicarious species • Vicarious species 



Verrucaria striatula subsp. borealis Santesson Verrucaria striatula subsp. australis Santesson 



(1939) (1939) 



Verrucaria cataleptoides Nyl. Verrucaria Racovitzae Vain. 



Staurothele clopima (Wbg.) Th. Fr. Staurothele gelida (Hook, and Tayl.) M. Lamb 



Subvicarious species Subvicarious species 



Verrucaria microspora Nyl. Verrucaria dispartita Vain. + I^- microspora Nyl. 



Verrucaria ceuthocarpa Wbg. Verrucaria tesselatula Nyl. + V. ceuthocarpa Wbg. 



Finally, one of the species. Derma tocarpon lachneum, appears to belong to the group to which the 

 name 'cosmopolitan' or 'ubiquistic' is applied. 



ECOLOGY 



In respect of habitat ecology, one group of Pyrenocarp lichens (comprising chiefly Verrucaria and 

 Arthopyrenia) is peculiar in being amphibious in the littoral zone (Santesson, 1939). Some of these, 

 like Verrucaria mucosa, are plants of the upper hydrohaline, intermittently submerged by the tide ; 

 others, of which V. maura is a good example, are more or less restricted to the lower hygrohaline or 

 spray zone, above the high tide level. V. mucosa has hitherto been regarded as one of the most marine 

 lichens, but in this respect it is now found to be surpassed by V. serpidoides (p. 20), a new species of 

 entirely marine habitat, never or only accidentally exposed to the air. 



On land also many Pyrenocarp lichens are characteristic of wet situations (fresh-water species). 

 Such are also found in the Antarctic, but there, on account of the peculiar climatic conditions, may 

 be actually in contact with liquid water for only a short period in every season (especially V. elaeoplaca, 

 p. 15). Some of the antarctic species of this hydrophyte group are also markedly nitrophilous, 

 absorbing ammoniacal decomposition products in solution from the snowmelt water with which they 

 are periodically inundated. 



