SYSTEMATIC ACCOUNT i, 



these two species, occurring at a low level in the littoral zone which would correspond in the Northern 

 hemisphere to the Fiiais vesiculosus-Balanus belt. 



Owing to the pronounced irregularity of the tides at Port Lockroy (they are seasonal rather than 

 diurnal) it is impossible to fix the position of the lichen in terms of 'high' or 'low' tide marks, and 

 difficult to assess the relative degrees of submergence and exposure. A series of observations was made 

 from 22 April to 24 May 1944; during this period exposure was noted only on 20, 21 and 22 May, 

 for a few hours daily. Towards the end of May the boat harbour froze over for the winter, and on 

 subsequent occasions, when the tide ebbed out sufficiently far to expose the lichen, the latter remained 

 covered by the ice layer. By the beginning of July the ice covering it was up to 75 cm. thick. After the 

 break up of the ice in late October a prolonged period of abnormally low spring tides set in, and the 

 lichen was regularly exposed for several hours each day. 



In the summer months V. psychrophila is most conspicuous on the boulders in the boat harbour 

 of Goudier Islet, blackening them with what looks from a distance like a sooty coating (PI. I, fig. i). 

 Seen from close quarters the colour is greenish blackish or olive-blackish (Ridgway, 191 2, p. xlvii, 

 25""m, pi. li, 23""'m). It also occurs on the solid rock at the other (southern) side of the islet, at the 

 same level. In its vertical distribution it is restricted to the hydrohaline and does not appear to overlap 

 either the lower zone of the permanently submerged V. serpidoides or that of the upper spray-zone 

 species (V. ceiithocarpa). The brown alga Adenocystis iitricularis occurs at the extreme base of its 

 vertical range. 



Santesson (1939) has pointed out that the degree of cracking in the thallus of the marine Verrucariae 

 is to some extent connected with the degree of submersion to which they are subject. The specimens 

 of V. psychrophila which I collected from the south side of Goudier Islet (no. 1220) have a much less 

 cracked thallus than those from the boat harbour ; the cracks are more sporadic, not joining up to 

 delimit distinct areolae. Although the vertical horizon is the same, it is possible that the lichen in this 

 relatively exposed position is more constantly wetted by wave action. 



As in several other marine Verrucariae, the thallus becomes brown after some time in the herbarium. 



Verrucaria Racovitzae Vainio (Fig. 3^; PI. IV, fig. 2) 

 1903, p. 38; Darbishire, 1923, p. 106. 



Not present in our collections. It occurs in west Graham Land: Palmer Archipelago, Moreno 

 Island (Vainio, loc. cit.), and also, fide Darbishire (loc. cit), on Elephant Island in the South Shetlands. 

 I have not seen Darbishire 's specimen. 



The holotype specimen in herb. Vainio (Exped. Antarct. Beige, no. 196 /)r. p.) is shown on PI. IV, 

 fig. 2. It is a small fragment of thallus about i cm. across, occurring together with V. elaeoplaca f. 

 glaiicoplaca, on fine-grained non-calcareous rock. Thallus o-i-o-2 mm. thick between the perithecia, 

 rimose or in places subcontinuous, the cracks (up to o-i mm. wide) occasionally reticulating to delimit 

 irregularly angulose areolae 0-5-1 -4 mm. diam. ; olivaceous-glaucescent or buff-coloured, i.e. approxi- 

 mately the same colour as the thallus of V. elaeoplaca, not changing when moistened ; surface smooth, 

 matt, not pruinose. A black hypothallus is visible in cross section, underlying the thallus. Cortex 

 present, pale brown or almost colourless, 9-14/^ deep, of ±isodiametric, thin-walled cells 2-3 /^ diam. 

 The whole depth of the thallus above the basal carbonaceous layer is filled with gonidial algae, which 

 are irregularly scattered, bright green, globose or angular, 8-1 1// diam., thin- walled. Fungal tissue 

 between algae hyaline, paraplectenchymatic, of thin-walled cells 2-3 /< diam. Perithecia numerous, 

 clothed by thallus almost to ostiole, forming hemispherical verrucae 0-7-0-9 mm. diam., with dark 

 brown or blackish circular apex o-2-o-3 mm. diam., slightly mamillate, with minute central pore. The 

 thallus clothing the perithecia contains a thin layer of gonidia. Excipulum globose or upright-oval in 



