:}16 DR. HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 
Of these, Mr. Ball is disposed to unite 1 and 2, and also 4, 5, and 6, making but three 
species in the above group, but distinguishing six sufficiently well-marked forms. 
B. muricella is in Europe confined to Scandinavia ; neither B. hirta nor rupestris are 
found in the Alps. 
Draba alpina, L. Regarding the numerous plants here brought together I have the 
following notes : 
B. alyida, Ad., according to specimens from Ledebour and Bunge, differs in no respect 
from B. alpina. 
B. pilosa, DC, is reduced to a synonym of B. alyida by Ledebour. I have no authentic 
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specimens of it. 
B. aspera, Adams, is placed by Ledebour in the section Aizoopsis, the species of which 
are eminently southern and oriental ; that author, however, had not seen the plant, and 
overlooks the fact of the distinguishing characters given by Adams being those of I). 
alpina. 
B. Adamsii, Led. (lasiocarpa, Adams), is described as differing from D. alpina in the 
pubescent pods, stellate hairs of leaves and scape, and small flowers ; but the pods of 
alpina are glabrous or pilose, and the other characters equally inconstant. 
B. glacialis, Adams. Of this there are five varieties described in ■ Flora Boreali- Ameri- 
cana.' It should be distinguished by the costa prominent in the under surface of the 
leaf ; but amongst a vast suite of specimens thus named I find the prominence of the 
costa to depend on the development of the leaf, and no characters that would serve to 
include those so distinguished, even as a permanent variety of alpina, L. Durand (Kane's 
Voy.) keeps glacialhs /3 distinct. 
B. pauciflora, Br. This was proposed by Brown as a doubtful species from Melville 
Island ; and I find, amongst starved specimens of B. alpina from that island, some that 
may be the plant that Brown alluded to. 
B. micropetala, Hook. This appears to me, without doubt, to be a starved form of 
alpina. It occurs only in very high northern latitudes, amongst the polar islands. 
Durand (Kane's Voy.) makes of it B. alpina, var. micropetala. 
B. trichella, Fr. Mr. Ball considers this to be probably a form of alpina. 
Draba androsacea, Wahl. (Lapponica, DC. an Willd. ?). This is a white-flowered 
species presenting as many puzzling forms as B. alpina, besides appearing to pass by 
insensible grades into hirta, rupestris, and muricella. Nor is it always possible to 
distinguish androsacea from alpina in a dried state, nor when the flowers of the former 
are bleached or vary to whitish, which they occasionally do both in the arctic circle and 
Himalaya. Of this plant B. Wahlenbergii, Hart., and lactea, Adams, are now generally 
acknowledged synonyms, as is B. nivalis, DC, non Lilj. 
B. crassifolia, Grah., has been referred by Mr. Ball (in Herb. Hook.) to lactea, Ad. 
{Fladnitzensis, Wulf), and certainly rightly. The yellow-flowered plant figured in ' Flora 
Danica ' is referable to alpina, L. 
B. Jlartinsunia, J. Gay. Of this species I know nothing accurately. 
B. oligosperma, Hook., is not different, I think, from the specimens marked Flcdnit- 
zensis from the Alps and Altai, and, further, is certainly a small form of androsacea, with 
