DR. LINDSAY ON THE LICHEN-FLORA OF GREENLAND. 311 



The Genera richest in Species are, therefore, in the order of their 

 richness — 



1. Lecidea. 5. Cetraria. 



2. Lecanora. 6. Umbiiicaria. 



3. Cladonia. 7. Squamaria. 1 



4. Parmelia. 8. Alectoria. j 



These are not necessarily, however, the genera richest in 

 individuals — the genera, therefore, which give a character to or 

 constitute predominant vegetation. There is insufficient evidence 

 to show what the latter genera are. All that can be asserted, on 

 the evidence of travellers, is, that in some localities the predomi- 

 nant Lichens and the prevailing vegetation are species of Umbiii- 

 caria or Placodium. There is no evidence that the Cladonice 

 occupy the same important position, as coverers of the soil, that 

 they do in Northern Scandinavia and Russia;* or that the Alectoi'ice, 

 Cetrarice^ and Parmelice occur in the same gregarious assemblages 

 that I have seen them do in Norway or Iceland.^ 



XXXVI.— On the Nature of the Discoloration of the 

 Arctic Seas. By Dr. Robert Brown, F.L.S., F.R.G.S. 



[Reprinted, by Permission, from the " Transactions of the Botanical 

 " Society of Edinburgh," vol. ix., pp. 244-252. Read De- 

 cember 12, 1867. Revised by the Author, March 1875.] 



The peculiar discoloration of some portions of the Frozen 

 Ocean, diiFering in a remarkable degree from the ordinary blue 

 or light green usual in other portions of the same sea, and quite 

 independent of any optical delusion occasioned by light or shade, 

 clouds, depth or shallowness, or the nature of the bottom, has, 

 from a remote period, excited the curiosity or remark of the 

 early navigators and whalemen, and to this day is equally a 

 subject of interest to the visitor of these little-frequented parts 

 of the world. The eminent seaman, divine, and savant^ William 

 Scoresby, was the first who pointedly drew attention to the 

 subject, but long before his day the quaint old searchers after a 

 North-West Passage " to Cathay and Cipango " seem to have 

 observed the same phenomenon, and have recorded their observa- 

 tions, brief enough it must be acknowledged, in the pages of 

 "Purchas — His Pilgrimes," or the ponderous tomes of Master 

 Hakluyt. Thus Henry Hudson, in 1607, notices the change in 

 the colour of the sea, but has fallen into error when he attributes 

 it to the presence or absence of ice whether the sea was blue or 

 green — mere accidental coincidences. John Davis, when, at 

 even an earlier date, he made that famous voyage of his with 



* See paper on the "Arctic Cladonise," p. 179. 



t " Flora of Iceland," p. 24 (Trans. Bot. Soc. of Edin., or Edin. New 

 Philosophical Journal, 1861) j " Northern Lichen-Flora," p. 403, ei seq. 



