OBSERVATIONS ON PARMELI A OLIVACEA. 
25 
older authors pro mux. p. To it are referable Mudd. Exs. n. 72, 
Leight, Nos. 263 and 356, and it is not uncommon in Great 
Britain and Ireland. The specific name aspidota Ach.Meth. (1803), 
p. 214 (ut var. P. olivacea) has priority to that of exasperata 
Ach. L. U. (1810), p. 645 ( Collema exasperatum ). 
3. Parmelia sub aurifera, Nyl. 
Although distinguished as a variety by Dillenius in Muse. t. 
21 f. 77c, this well marked species was very strangely overlooked 
by authors till it was definitely indicated by Nylander in 
Flora 1873, p. 22. It may at once be recognised by the yellow 
medulla and the small yellowish soredia with which the 
thallus is efflorescent. The medulla in our specimens, as in all 
more southerly regions where it occurs, is less distinctly yellow 
than those from Scandinavia, and the apothecia are extremely rare. 
The spermatia are shorter than in the two preceding species. It 
is apparently a somewhat local plant in Great Britain. 
4. Parmelia prolixa, Ach. 
Though usually regarded as a variety of P. olivacea , in the 
older and inaccurate conception of that species, this is well en- 
titled to be regarded as distinct, on account of the character of the 
laciniae and the much smaller spores. It is apparently a rare 
British plant, occurring chiefly in W. England, and sparingly 
amongst the N. Grampians of Scotland. To it is referable Leight. 
Exs. n. 365. 
5. Parmelia prolixa* Delisei, Dub. 
This is distinguished, though most probably only as a sub- 
species, by the paler thallus, the broader laciniae, and by the re- 
action of the medulla with Ca. Cl. being at length To it is 
referable P. olivacea , var. aquiloides , Linds., and it is represented 
by Leight. Ays. n. 291 prop. Apparently it is a rare and local 
plant in Great Britain and Ireland, 
var. isidiascens, JVyl. 
This is characterised by the peculiar crowded verrucaeform 
isidia, with which the thallus is sprinkled. Like the type, it is 
a rare British plant, having been detected only in W. England 
and Central .Scotland. It is represented by Leight. Exs. n. 291 
prop. 
6. Parmelia prolixa* sorediata, Ach. 
This is distinguished by the smaller thallus, which is sprinkled 
towards the centre with whitish or brownish -white verrucose 
soredia. In other respects it agrees with P. prolixa , so that it is 
scarcely to be regarded as a distinct species. It is apparently of 
extremely rare occurrence in the Highlands of Scotland. 
7. Parmelia fuliginosa, Fr. 
From all the preceding this may readily be recognised by the 
peculiar isidia with which the thallus is densely clothed. 
In addition to this the re-action of the medulla with Ca. Cl. 
sufficiently entitles it to be regarded as a distinct species. It is 
probably not uncommon in the mountainous regions of Great 
Britain on rocks, trees, and old pales. 
