12 DISCOVERY REPORTS 



bh. Thallus rimose. 



10 a. Cracks black. 



iirt. Thallus uniformly tesselate-areolate with areolae 0-5-1 -o mm. diam. V. tesselatitla 



1 1 h. Thallus not areolate, but with gaping cracks often reticulating to delimit irregular 



areas of variable size (i-io mm.) ... V. tesselatula f. dermoplaca 



[Thallus composed of confluent microthalli separated by blackish lines and 

 simulating large flat areolae ... ... ... V. elaeoplaca f. glaucoplaca] 



loh. Cracks between areolae! concolorous with rest of thallus. 



iia. Areolae up to i mm. diam. ... ... ... ... ... ... V . ceuthocarpa 



1 1 h. Areolae larger. 



12a. Thallus bufT-brown or olivaceous-glaucescent; spores usually 14-18 x S-ii/x; 



fresh- water species ... ... ... ... ... ... ... V. elaeoplaca 



izb. Thallus olive-blackish; spores 1 1-13 (-15) x 6-7/^1; marine species... V . psychrophila 



Verrucaria ceuthocarpa Wahlenberg (Fig. 36). 



apud Acharius, 1803, suppl. p. 22; Vainio, 1909, p. 163, 1921, p. 72; Zschacke, 1934, p. 194. 



West Graham Land. Palmer Archipelago : Port Lockroy, Goudier Islet ; east and south-east sides of 

 islet, on basalt dykes about i m. above high-water level, in the rough weather spray zone; F.I.D.S., 

 23. iv. 1944 (no. 1227); 28. xii. 1944 (no. 21 19); on granodiorite face slightly above high-water level, 

 in the spray zone; F.I.D.S., 23. iv. 1944 (no. 1222 pr. p.). 



Forming effuse, indeterminate, discontinuous patches. Thallus thin, olivaceous-blackish, entirely 

 rimose-areolate, with areolae o-3-o-7 mm. diam. The specimens more or less correspond to the typical 

 form of the species (var. areolatodijfracta Vainio, 1909). Perithecia minute, not over 0-2 mm. diam., 

 with prominent, almost hemispherical, black apex. Excipulum colourless below and at sides. Spores 

 9-12 X 6-7//. 



Geographical Distribution. New to the Eu-antarctic zone ; previously recorded from northern 

 Europe, Spitsbergen, Bear Island, Novaya Zemlya, north-east Siberia, Bering Strait, Greenland, 

 North America (Maine and Massachusetts), and in the southern hemisphere, Kerguelen (Miiller 

 Argoviensis, 1884, p. 139^). According to Lynge (1937, p. 13), it is the commonest marine Verrucaria 

 in the Arctic. 



Var. deformata Vainio 

 1909, p. 164. 



West Graham Land. Palmer Archipelago: Port Lockroy, Goudier Islet; south side of islet, 0-5- 

 1-5 m. above high-water level, on granodiorite rock face in the rough weather spray zone; F.I.D.S., 

 23. iv. 1944 (no. 1222); 25. iv. 1944 (no. 1223); 7. i. 1945 (no. 2190). 



' Thallus sat crassus, areolatus aut areolato-diffractus, areolis difformibus, majoribus vel minoribus, 

 saepe leviter inaequalis et habitu quasi morbosus, olivaceo- aut pallide-olivaceo- et nigricanti-variegatus, 

 opacus' (Vainio, loc. cit.). I have not seen an authentic specimen of this variety, but if I am correct in 

 referring the present specimens to it, the ' morbose habitus ' and pale olivaceous variegation mentioned 

 by Vainio is due to numerous algal efflorescences on the thallus caused by proliferation of the thalline 

 gonidia. These scattered, olivaceous-greenish, soredia-like, erumpent, mealy-granulose outgrowths are 

 o- 1 5-0-30 mm. diam., and in sections through the thallus are seen to be masses of gonidial algae in a 

 state of rapid multiplication, forming pairs, tetrads, and octants, and rupturing the thalline cortex in 

 emerging. They are not accompanied by hyphal filaments, and hence cannot be classed as soredia. 



1 Miiller, loc. cit., quotes the Kerguelen locality as being 2000 feet above sea level, which makes the record seem improbable. 



