DR. LINDSAY ON THE LICHEN-FLORA OF GREENLAND. 293 



The difference between the Greenland and Arctic- American 

 Lichen-floras is obvious from a comparison of the summary 

 appended to my Catalogue of the former with Leighton's similar 

 summary of the latter (p. 185). But comparisons based on such 

 tables alone are most fallacious, inasmuch as they are drawn up 

 on very different principles. Leighton, for instance, gives 35 

 genera, while I give only 28 ; the number of species and varieties 

 in Greenland being 268, and in Arctic America 203. My genera 

 are fewer, however, mainly because I do not split up such genera 

 as Collema, Cladonia, Usnea^ Alectoria, Cetraria, Nephroma^ 

 Pai'melia, Physcia, Squamaria, Lecanora^ Lecidea, Endocarpon, 

 and Vcrrucaria into the host of sub-genera into which they have 

 been divided of late years by Continental Lichenologists. Another 

 class of discrepancies necessarily arises from the different position 

 given to certain anomalous species, such as Lecanora or Pertu- 

 saria bryontha, Thamnolia or Cladonia vermicularis, Endocarpon 

 viride or Normandina viridis. Richardson's Lichens, according 

 to Leighton, amount to 163 (p. 184) — a number which does not 

 correspond with the total given in his table or summary (p. 185). 

 But he names or numbers a series of trivial or inconstant forms 

 or conditions, which in the hands of some other lichenologists — ■ 

 certainly in mine — would not receive separate nomenclature or 

 enumeration.* Treated in a similar way, the number of species 

 and varieties given in the following Catalogue of Greenland 

 Lichens would be largely increased, for I have neither named nor 

 numbered the " various forms " or " several forms " of many 

 variable species {e.g.) of the genera Cladonia, Parmelia, Physcia, 

 Lecanoi'a, and Lecidea. 



Leighton's enumeration, however, is very far from giving an 

 adequate idea of the Lichen-flora of the vast area known as Arctic 

 America. Its deficiencies may be judged of by the number of 

 species mentioned in other works or herbaria as Arctic-American 

 Lichens that are not enumerated by Leighton. Thus Tuckerman 

 in his " Synopsis," published in 1848, records the following, 

 which do not occur in Leighton's list : — 



Trachylia tigillaris. Ramalina polyraorpha. 



Calicium lenticulare, Ach. ; sub- Dufourea ramulosa. Hook, 



tile, Pei's. ; phaeocephalum, Cetraria odontella ; aculeata. 



T. ^ B. Solorina crocea. 



Cladonia alcicornis ; carneola ; Nephromium arcticum ; resu- 



turgida, Hffm. pinatum, Ach. 



Sph^rophoron fragile ; globi- Parmelia tristis ; Fahlunensis ; 



ferum, L. ; compressum, caperata ; conspersa ; diver- 



Ach. sicolor, Ach. 



Alectoria ochroleuca and var. Physcia parietina, vars. poly- 



rigida ; jubata, var. bicolor ; carpa, Fr., and laciniosa, 



implexa, Fr. Diif. 



* His elaboration of the genus Cladonia may be taken as an illustration, 

 and compared with my remarks on that genus in my " Arctic Cladonige," 

 Trans. Bot. Soc. of Edin., vol. ix, p. 179. 



