Diplotomma canescens
≡Diploicia canescens (Dicks.) A.Massal., Ric. Lich. Crost.: 86 (1852).
≡Lichen canescens Dicks., Fasc. pl. cryptog. brit. 1: 10 (1785).
Description : Flora (1985: 159).
Chemistry : Diploicin (major), dechlorodiploicidin, 3-dechlorodiploicin, atranorin and chloratranorin, secalonic acid A, B, C.
K: Raoul I. N: Northland (Tokerau Beach Karikari Peninsula, Puheke, Poor Knights Is, Lady Alice I., Little Barrier I.), South Auckland (Onemana Beach). S: Marlborough (Chetwode Is., Goose Bay), Otago (Black Head). On coastal rocks. Ch: On loose bryozoan limestone outcrops near quarry "Big Bush" 40 m asl. Known also from Great Britain, Europe, North and South America and Australia (Purvis et al. 1992; Nimis 1993; Santesson 1993; Esslinger & Egan 1995; McCarthy 2003c, 2006; Nimis & Martellos 2003; Santesson et al. 2004).
Cosmopolitan
Illustrations : Jahns (1980: 247, pl. 622); Phillips (1987: 171 – as Buellia canescens); Wirth (1987: 185; 1995a: 377); Dobson (1992: 137; 2000: 150; 2005: 1655 – as Diploicia canescens); Brodo et al. (2001: 303, pl. 311); Sérusiaux et al. (2004: 78 – as Diploicia canescens).
Diplotomma canescens is characterised by: the saxicolous habit; the squamulose, subcrustose, placodioid, white or grey-white thallus with distinctively plicate, thickened margins; convex lobes that are distinctly pruinose and sorediate; soredia in laminal soralia, white, coarsely granular to farinose.
