LICHENS AND LICHEN. PARASITES

DODGE-LICHENS AND LICHEN PARASITES 177
Apothecia sessile, amphithecium well developed, with Stigonema colonies as well as Protococcus;
paratlieciuni poorly developed and inconspicuous; hypothecium well developed, hyaline;
paraphyses slender, branched and moniliform above; asci 8-spored; ascospores ellipsoidal,
unicellular, hyaliile, thin-walled. Spermogonia ovoid, wall thin, hyaline, liymenium iilvaginating ;
spermatiophores long ; spermatia relatively short, bacilliform.
In this genus the iiiternal cephalodia reach such a high developmeilt tliat it is difficult to find
any Protococcus in many sectioiis. The habit of our Kerguelen specie; is quite similar to Panmria
clichroa, although the colour is much deeper orange and the spore is thin-walled. Sterile material
may easily be mistaken for Pannaria.
PLACOPSIS BICOWR (Tuck) B. de Lesd.
Placopsis bicolor (Tuck.) Bouly de Lesdain, Ann. Crypt. Exot., 4, 100; 1931.
Placorli~tnt bicolor Tuclr., Bull. Torrey Bot. Club, 6, 57 ; 1875 : Bull. 1J.S. Nat. M'is., 3, 28 ; 1876.
Lecanol-a bicolor Zahlbr., Deutsche Siidpolar Exp., 8, 48 ; 1906.
Lecanora, gelida Hoolr. f. & Tayl., London J'our, Bot., 3, 641; 1844: Hook. f., Crypt. Antarct., 229;
1845 : F1. Aiitarct., 2, 535; 1847 : Crombie Rept. Sci. ~esults Voy. "Challenger" Bot., 1, 2,
234 ; non Ach.
Placopsis gelida Crombie, Jour. Linn. Soc. bot., 14, 184 ; 1876 : Jour. Bot. Brit. For., 15, 104, 106 ;
1877 : Phil. Trans. Roy. Soc. [London], 168,48 ; 1879.
Lecanora (PlacopsGs) gelida f. k.teritia Nyl. ap. Crombie, Jour. Linn. Soc. Bot., 15, 184; 1876:
Phil. Trans. Roy. Soc. London, 168,48 ; 1879.
Pla.codiwnt gebidwnt v. lateritium Wilson, MBm. Herb. Boissier, 18, 87 ; 1900.
Type : Icerguelen, Molloy Point, J. H. Kidder (U.S. Transit Venus Exp.), type of L. gelida f.
lateritia from Icerguelen, Swain's Bay, A. E. Eaton (Venus Transit Exp., not seen). Following
description based on type, with description of spermogonia from sterile specimen from Ker-
pelen, Christmas Harbour, J. D. Hooker (Voy. " Erebus & Terror ") , originally detrrn~iiied
as Lecanora gelida Ach. and annotated by Tuckerman as L. gelida var. lateritia Nyl.
Thallus orbicular, determinate, margin shortly crenate lobed, lobes about 2 mm. long and broad,
rest of the thallus cracked into polygonal areoles about 1 mm. ill diameter; now (1940) burnt
sienna, about 500p thick; cortex 35p thick, a palisade of thick-walled pseudoparenchyma ; algal
layer about 140p thick, of scattered cells and small colonies of Protococcus with spherical cells
about P5p in diameter, largely replaced by a palisade of Stigmema filaments 7-8p in diameter,
closely septate as internal cephalodia; medulla of subvertical looser hyphae 34p in diameter;
external cephalodia flattened conic, 2-3 mm. in diameter, striate rimose nearly to the centre aitd
crackling along the striate suggesting apothecia of Coccocarpia) to almost depressed cerebriform ;
cortex similar to that of the thallus, consisting of more or less ellipsoidal colonies of Stigonema,
sometimes clearly filamentous, about 7p in diameter, sometimes separated into single more rounded
cells 7-8p in diameter and separated by partitions of periclinal, congultinate hyphae 20-35p broad,
Apothecia up to 3 mm. in diameter, sessile, constricted below, margin elevated, smooth, cortex
often eroding so that the margin appears whitish, disc black, plane; amphithecium 110-120p thick,
extending in a layer 35p thick over the thecium in the juvenile state and gradually retreating as
the thecium coiltinues to grow ; cortex continuous with that of the thallus and of the same texture ;
algal layer filling the rest of the amphithecium ; parathecium not differentiated; hypothecium
150p thick, thinning to 35p thick at the edge, of densely woven, slender, deeply staining hyphae;