SYSTEMATIC ACCOUNT 



27 



Family MASTODIACEAE 



Genus Mastodia Hooker f. and Harvey, 1847 



Mastodia tesselata (Hooker f. and Harvey) Hooker f. and Harvey (Fig. 3 m ; PI. HI, fig. i ; PI. IV, fig. i) 



apud Hooker, 1847, p. 499, pi. cxciv, fig. ii; Vainio, 1903, p. 36, pi. iv, figs. 33, 34, 1909, p. 156; Hue, 1909, 



P- 315. %s. 1-5, 1915, p. 13; Darbishire, 1912, p. 41, pi. 3, fig. 36. 

 Ulvella tesselata Hooker f. and Harvey, 1845, p. 297. 



Prasiola tesselata Kiitzing, 1849, p. 473; Hariot, 1889, p. 29, pi. 2, figs. 1-6; Knebel, 1936, p. 45. 

 Leptogiopsis complicatula Nylander, 1884, p. 211. • 

 Laestadia prasiolae Winter, 1887, p. 16 (fungus). 

 Guignardia prasiolae Reed, 1902, p. 150 (fungus). 

 Dermatomeris Georgica Reinsch, 1890, p. 425. 



South Shetlands. King George Island : Admiralty Bay, Martel Inlet ; on fine-grained non-calcareous 

 rock ; Discovery 1933-5, 18. xii. 1934 (no. 1481-15); Esther Harbour, east side, slightly above sea-level; 

 Discovery 1935-7, 6. i. 1937 (no. 1949-3). Deception Island: north side of crater to west of the whaling 

 settlement, altitude c. 60 m., on andesitic stones on scree slope; F.I.D.S., 8. ii. 1945 (no. 2318 pr. p.). 

 Clarence Island: Cape Bowles; Discovery 1935-7, ^3- ^i- ^93^ (no. 1874-4). 



West Graham Land. Palmer Archipelago: Port Lockroy, Goudier Islet; near summit of islet, 

 altitude c. 7 m., on granodiorite rocks; F.I.D.S., 29. ii. 1944 (no. 1151), 28. xi. 1944 (no. 1833), 

 14. i. 1945 (no. 2234 pr. p.), 18. i. 1945 (no. 2256 pr. p.) ; on weathered wooden deck of old whaling 

 scow on beach; F.I.D.S., i. iv. 1944 (no. 1214). Mainland coast between Cape Renard and Cape Bellue: 

 opposite Berthelot Islands; at foot of cliffs, on granitic rock; B.G.L.E., 27. vii. 1935 (no. 1188-1). 

 Argentine and neighbouring Islands : Berthelot Islands ; on north-facing granitic low sea cliff, altitude 

 5 m. ; B.G.L.E., 18. iii. 1935 (nos. 1094-34, 1094-45). Galindez Island; on non-calcareous rock; 

 B.G.L.E., 23. xi. 1935 (no. 1263-2). Trinity Peninsula, north coast: Cape Roquemaurel ; on north-east- 

 facing non-calcareous rocks, altitude 16 m. ; Discovery 1933-5, 20. i. 1935 (no. 1490-2). 



East Graham Land. Trinity Peninsula, south coast : Hope Bay ; near Boeckella Lake, altitude c. 60 m., 

 on non-calcareous rocks and stones; F.I.D.S., 15. iv. i945(nos. 2366, 2368/)r./)., 2369 pr./)., 2372 /)r./).); 

 on stones at side of frozen shallow freshwater pool in the penguin rookery; F.I.D.S., 15. iv. 1945 

 (no. 2363 pr. p.). 



This organism has been classified by different authors as a lichen, an alga, and a fungus. The algal 

 component is Prasiola crispa. 



It is the commonest Pyrenocarp lichen in the Graham Land sector of the Antarctic. Skottsberg (1912) 

 has observed its transition into the free-living Prasiola crispa, and I saw this also on Goudier Islet. 

 One of the features which speaks most strongly in favour of Mastodia being a true lichen is the vigour 

 of the dual organism, and in particular its ability to withstand desiccation better than the free-living 

 Prasiola. On Goudier Islet Mastodia tesselata covers large areas of the exposed smooth granodiorite 

 rocks, an arid habitat throughout the whole of the summer, except for an occasional light fall of snow 

 or sleet ; the plants are nearly always completely dry and brittle to the touch. Prasiola crispa, on the 

 other hand, ahhough it can become desiccated for short periods without injury, is much more dependent 

 on a supply of fresh water, and for this reason occurs only in hollows and crevices in the rocks where 

 water tends to flow or accumulate. 



Both Mastodia and Prasiola are highly nitrophilous, occurring in rookeries or on bird-rocks where 

 an abundant supply of nitrogenous matter is available from bird excrement dissolved in snowmelt 

 water. P. crispa is one of the most nitrophilous plants known, occurring even around the nests in 



