42 ANNALS OF SCOTTISH NATURAL HISTORY 



a mixture of Surrey soils. " These plants have entirely lost 

 their original colour and have become completely green, so 

 that it appears that the only character which separates this 

 variety from the type, is merely temporary and due to habitat. 

 The serpentine gravels of Unst contain a number of minerals, 

 notably chromate of iron, and the colour of the leaves may 

 probably be due to the influence of one of them." Ostenfeld, 

 also in Hit., says the Unst plant " has no systematic value " 

 apart from the mountain plant. Therefore there is no need 

 to keep up a name to distinguish the alpine from the Balta 

 Sound plant 



In "Journ. Bot." 386, 1898, Mr. F. N. Williams stated 

 from an examination of authentic specimens, I believe this 

 to be a hybrid between two forms of alpinum. This cannot 

 be the case since nigrescens is found where C. alpinum is 

 absent as at Unst, and in other places in Scotland. While 

 Mr. N, E. Brown, in " Suppl. to 3rd ed. of E.B. 42, 1891," 

 says, " On comparing the seeds of typical C. latifolium with 

 those of the British plant arcticum, including var. Edmonstoni, 

 I do not find any difference of kind, but only a difference of 

 degree, the seeds of the British plant are smaller than those 

 of typical C. latifolium, although considerably larger than those 

 of C. alpinum, but the testa of thoroughly ripe seeds is loose, 

 although nothing like so inflated as in C. latifolium ... so 

 that I think our plant is really C. latifolium, but a form with 

 smaller seeds, for which the varietal name SmitJiii, Syme, 

 may be retained. Mr. F. N. Williams, " Journ. Bot." p. 493, 

 1898, says, "I have examined the material indicated by 

 Mr. N. E. Brown, and am disposed to concur with him in 

 adding C. latifolium to the British Flora. I do not, however, 

 agree with him in identifying C. arcticum with C. latifolium, 

 var. Edmonstoni, though there may be some difficulty in 

 distinguishing them in the dried state. All the more reason 

 is there against according to C. arcticum specific rank." 



I think, however, we may safely separate as a species C. 

 nigrescens, Edmonston, from the continental C. latifolium, as, 

 in addition to the seed characters alluded to there are other 

 differences which are sufficient to give it specific value, and 

 as Syme ("E.B." ii. 88) says, " it is very doubtful if [this 

 is] the C, latifoliiim of Linnaeus." 



