LICHENS AND LICHEN. PARASITES

B.A.N.Z. ANTARCTIC. RESEARCH EXI'EDITION
Surface slightly rugose and subfoveolate
Not verrncose, with somc black annular cracks; soralia eroded, flat U. yicat?~
Verrucose, without annular cracks; soredia minute, on tips of the warts
U. Crontbii
Densely papillate . . . . . . . . . . Ti. granzilifera
Fertile
Coarsely verrucose and rugose, often somewhat angulate ; not sorediose
U. ntelaxanthci
Minutely tuberculate, not Tugose or angled, soredia abundant U. floriforntis
USNEA LAXISSIMA Dodge, sp. nov.
Type : Queeii Mary Land, Possession Nuiiatak, C. T. Harrisson, A.A.E. 84.
Thallus 4 cm. altitudine vel major, siccitate fragillimus, dichotome ramosus, internodis longis,
ramis divergentibus, basi subconstrictis, mollis, nitidus, nigroannulatus sed non annulatim fractus,
isabellinus, ramis majoribus subarticulatis articulationibus constrictis, fractis, irregulariter
foveatis, raro subscrobiculatis; ramis ultimis longis, tenuissimis; eramulosus, teres; soredia rars,
punctiformia, pseudocyphellis minutis simulantia, alia subconvexa tuberculiformiave, ad 0.3 mm.
diametro, farinosa, viridia ; cortex 25-30p crassitudine, gelifactus, hyphis in 7,~ exteris hyalinis,
psgudoparenchymaticus, cellulis isodiametricis, crystallis luteis minutis nubilatis ; algae in coloniis
parvis sub cortice, cellulis 5-7p diametro; medulla ca. 185p crassitudine, K-, hyphis 5 ,~ diametro,
pachydermeis, crystallis hyalinis nubilatis, ex axi radiantibus, dichotomis in rete laxissimo
dispositis ; axis chondroideus ca. 16OP diametro, sectione transversali orbicularis, hyphis longitudinalibus,
pachydermeis, conglutinatis.
Thallus at least 4 cm. tall, very fragile when dry, dichotomous, internodes long, branches
divergent, often somewhat conetricted at the base, very soft, shining, black annulate but uot craclrecl
at the annulations, isabella colour, larger branches somewhat articulate, constricted at the joints,
cracked and separating showing the axis,'irregularly foveate, rarely almost scrobiculate, ultimate
branches long, very slender; eramulose, terete ; ~oredia rare, punctiform, less than 0-1 mm. in
diameter, suggesting minute pseudocyphellae, occasionally slightly convex, tuberculiform up to
0.3 mm. in diameter, farinose, glass green; cortex 25-30,u thick, ge'lified, the outer 7,~ hyaliue,
pscndoparenchymatous of isodiametric cells 3-4 rows thick, heavily incrusted with minute
yellowish crystals; algae in small colonies just below the cortex, cells 5-7p in diameter; medulla
a very loose net of hpphae 5p in diameter, very thick-walled, nubilated with larger hyaline crystals,
radiating from the chondroid axis, divergently dichotomously branched, leaving very large air
spaces ; chondroid axis about 160p in diameter, circular in cross section, of conglutinate longitudinal
thick-walled hyphae.
Although this species seems to have been growing on greatly weathered red granite from the
small grains tangled in the thallus, I have been unable to find it attached, and the lower ends of
many plailts are blackened and decomposing, as if it were dying at the base and proliferatiag at
the tip, a condition unknown to me in any other species of Usnea, although not uncomrnoii in other
groups of lichens. On the othet.. hand, it may have been torn loose from its base by high winds
.-
and colltinued to develop in some more protected situation between the roclrs. It is EO soft that
it cannot have been erect, probably decumbent or perhaps pendulous, if attached to a vertical
surface of rock.
The relationships of this species are not clear. In microscopic structure it seems closest to
U. frigida Dodge & Balrer, an erect plant from Marie Byrd Land, with much more conspicuoi~s