LICHENS AND LICHEN. PARASITES

U.A.N.Z. ANTARCTIC RESEARCH EXPEDITION
USNEA [Hill] Wiggers.
Usnea [Hill] Wiggers, Primit. F1. Holsat., 90; 1780.
Usnea Hill, Gen. Nat. Hist., 2, 85; 1751 [Hist. Pl.].
Parnaelia sect. Usnea Wallr., F1. Crypt. Germ., 3, 541 ; 1831.
Type : U. flo~idu (L.) Wigg.
Thallus fruticose or filamentous, very rarely of a single branch, usually of several compound
branches, dichotomous or subdichotomous, more rarely sympodially branched, from 1 cm. to 7 m.
or more long, erect, pendulous or prostrate, attached to the substrate by a hapteron; branches
thicker at the base, thinning very much toward the apex, 0-2-7 mm. thick, terete, angled or
longitudinally sulcate, or foveolate, smooth or tnberculate, verrucose or spinuliferous, continuous,
areolate or annulate; cortex coriaceous or somewhat spongy, of densely woven thick-walled,
conglutinate, vertical hyphae, in a few species almost evanescent on the primary branches; algae
usually protococcoid (apparently Trentepohlioid in the section Rocce!linw) ; medulla usually well
developed, quite variable in thickness ; chondroid axis, single, percurrent, of longitudinal, thickwalled
hyphae, usually very solid, rarely lacerate on the surface or hollow. Apothecia lecanorinc.,
constricted at the base, lateral, rarely subterminal or terminal, margin usually thin, nude or
ciliate ; asci subcylindric or slightly inflated ; ascospores unicellular, hyaline, ellipsoidal, epispore
distinct ; paraphyses conglutinate, septate, branched, epithecium with distinct granules. Spermogonia
immersed in the cortex, pale or slightly darkened, spermatiophores sparingly septate; spermatia
straight, with one slightly thicker.
The genus is divided into six subgenera of which only Neuropogon and Ewusnea reach our
area.
Subgenus NEUR~PO~ON (Nees & Fw.), Motyka.
Usnea subgenus Newopogon Motyka, Lich. Gen. Usnea Stud. Monogr. Syst., 1,18; 1936.
ATeuropogon Nees & Flotow, Linnaea, 9,496 ; 1835.
Usnea sect. Nez~ropoyon Mont. in Gay, Hist. Fis. Polit. Chile, Bot., 8, 67; 1852.
Type : Montagne treated N. nze!azanthtls (Ach.) Nyl. as the type of his section Neuropogon of
Usnea arrd was followed by Motyka when the section was rai~ed to snbgeneric rank. As a genus,
Nezcropogmt was based on hT. Poeppigii and N. antel~tarius. Nylander, Syn. Meth. Lich., 1, 275;
1860, t~ansferred N. Poeppigii to Clzlorea, leaving N. antennarius as the type of the genus. The
latter is now considered by Motyka and Lamb as a synonym of N. azcrantiaco-ater (Bory) Lamb.
Thallus short, not reaching 10 cm., fruticose, erect, branched, almost wholly saxicolous,
sulphur yellow, orange or orange red, tips of branches and cilia of apothecia when present,
commonly black, or whole thallns black or black variegated. Apothecia lateral on smaller
branches (often appearing terminal as the tip of the branch is small and inconspicuous in most
cases), disc usually black (disc zinc orange to tawny, irregularly blackening in U. trachycarpa).
While the habit and colour of this subgenus are usually easy to recognize, the various structures
of the individual species show such close relationships to those of other subgenera, I cannot follow
Lamb, Jour. Linn. Soc. Bot., 52,199-237 ; pl. 5-11 ; 1939 in regarding it as a separate genus. Except
for a single commonly recognized species in the Arctic and Andes, all of the species are antarctic
and subantarctic.