Jone 1905.] | BOTANICAL SOCIETY OF EDINBURGH. 107 
Placodium elegans (Ach.) Nyl.—Cosmopolitan, Arctic, and 
typically Alpine. Good fertile specimens were found on 
rocks on the $.W. shore of Scotia Bay, South Orkneys. 
Placodium fruticulosum (Darbish.) nov. sp.—This is a new 
species, and I will therefore preface my observations concern- 
ing it by its diagnosis. Thallus fruticulosus, basi substrato 
affixus. Protothallus gonidiis destitutus, chondroideus, margo 
effusus et hyphis instructus solitariis vel conglutinatis. 
Podetia fruticulosa, ad marginem thalli prostrata et leviter 
compressa, inferne albida, nondum substrato affixa nisi proto- 
thallo; ad centrum thalli erecta, 1-2 cm. alta, dichotome 
sed irregulariter divisa, 1-1-5 mm. crassa, ad apices bene 
divisa; apices juxtapositi thallum crustaceum simulantes ; 
aurantiaca aut flavescentia KHO purpurascentia; stratum 
corticale hyphis instructum transversalibus, cuticulo valde 
distincto obtsectum 6-8 yw lato; stratum medullare dense 
stupteum. Gonidia protococcoidea, Apothecia lecanorina, 
1-4 mm. lata, emergentia, sed adpressa, lateralia; amphi- 
thecium distinctum, gonidiis instructum ; parathecium decolo- 
ratum; epithecium flavescens aut aurantiacum, KHO pur- 
purascens; hypothecium decoloratum, strato gonidiali inferne 
instructum ; thecium 90-100 mu crassum; paraphyses sim- 
plices, apice cellulis brevibus terminantes; axi cylindrici, 
elavati 10 u lati; sporz octone hyaline bicellulares orculi- 
formes, 5-6x11°5 w~ magne. Spermogonia et soralia non 
visa. Habitat ad saxa, S. Orkneys. 
Placodium fruticulosum was tound growing on rocks around 
Scotia Bay, South Orkneys. It is apparently very common 
from the shore right up to the summit, evidently representing 
an important constituent of the lichen vegetation. The 
podetia are fruticulose and erect, branching frequently and 
in an irregular way. ‘The tips of the branches, however, are 
pretty much of the same height, and being very closely applied 
to one another, this lichen appears to be crustaceous. The 
exposed parts of the plant are light yellow or orange coloured, 
but those more hidden are paler, and in part even white. 
The lowest portions of the podetia can obtain a thickness of 
about 1°5 mm., the tips being as much as 1 mm. across. The 
podetia measure up to 2 cm. in height, and are generally 
cylindrical in section near the margin. Near the margin of 
the whole thallus, they generally assume a more typical 
