29S J. A. MARTINDALE : NOTES ON BRITISH LICHENS. 



But now come the questions : What is the ' olivacea ' of these 

 difterent works ? and which of the species is intended by any record 

 of ^ P. olivacea^ we may find in them or in local lists of plants? And 

 in trying to answer these questions we must remember that all the 

 writers mentioned speak of their particular ^olivacea' as quite a 

 common plant. Well, a little reflection shows that a different answer 

 must be given to the first question for most of these authors, and 

 may be required for the second according to the date of the record. 

 If we restrict ourselves to English and probably Irish plants, ex- 

 cluding Scotch ones altogether from consideration, we may safely say 

 for all authors and records that true olivacea was never intended ; for 

 as Mr. Crombie has pointed out in his paper on ^P. olivacea and its 

 allies' (Grevillea, vol. x, p-. 24) the true plant 'is essentially a boreal 

 species which is met with only very rarely in the Scottish Highlands.' 

 P. sorediata also has, so far as I know, not been gathered in South 

 Britain, and P. isidiotyla only recently detected in Cumberland and 

 Westmorland. Both of these, or at all events the latter, may be 

 found to have a wider range, but it is very unlikely that any specimen 

 of them had been seen by the earlier English botanists. We may, 

 then, in all probability consider Hooker's and Taylor's ' olivacea ' to 

 be an aggregate species made up of exasperata^ prolixa, Delisei^ 

 fuliginosa^ and subaii?'ifera. jMr. Crombie states that exasperata was 

 chiefly intended by earlier authors, and it is the plant figured in 

 English Botany, 2180; but though widely distributed it cannot be 

 said to be common, and it has even been called rare by Mr. Crombie 

 himself (Lich. Brit, p. 35). Very likely it was held to be the most 

 perfect development of the species, but certainly we require the 

 addition of the others to justify the supposed common occurrence 

 of their ^olivacea.' 



Mudd's ' olivacea ' is, of course, more restricted in consequence of 

 his distinguishing Delisei and fuligi?iosa under separate names ; and 

 it seems to be probable that his type was made up of exasperata, 

 S2tbaurife7'a, and prolixa. The second of these plants is widely 

 distributed and in some places very abundant, though frequently 

 more or less atypical. Crombie's ' Lichenes Britannici ' is merely a 

 list of species believed to compose the British lichen-flora. It was 

 the first attempt, after a lapse of nearly twenty years from the pub- 

 lication of Mudd's Manual, to enumerate the lichens native to Britain, 

 and was of great value at the time when it appeared. The stations 

 recorded for each plant were, of course, in great part gathered out of 

 previous writers, and no doubt P. olivacea was recorded in it as 

 common in Britain on the faith of old statements, but these records, 

 as we have seen, had reference to other plants. 



Naturalist, 



