DR. HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 329 



in wliicli the petals are often as short and of the same shape as in Rupreeht's plant, and 

 the cauline leaf wanting. I doubt much if P. Kotzebwei is really distinct. 



Saxifraga Alzoon, Jacq. Koch, Pries, and most authors keep this distinct from S. 

 Cotyledon ; but I must own that I cannot satisfactorily discriminate their forms or make 

 them tally with their assigned habitats, and am thus obliged to treat them as one plant. 

 Both, according to Fries, grow in Lapland and Western Europe generally. Cotyledon 

 alone is stated to be Icelandic : Aizoon, which alone is Greenlandic, Labrador, and N. 

 American, is nowhere stated to occur in the Russian dominions. 



S. ccBspitosa, L. It is not my purpose to enter into the disputed question of the limits 

 of the members of this aggregate collective species. I have repeatedly examined all, and 

 found innumerable grades connecting the most dissimilar, such as exarata and sileni- 

 flora. Almost all are high arctic. 8. uniflora is the same as venosa, and is referred by 

 Torrey and Gray to ccespitosa, to which ^S*. Groenlandica is reduced by almost all authors. 

 S. exarata, Vill., is kept distinct in ' Elor. Bor.-Am.' (with an appended observation 

 regarding the difficulty of distinguishing it), as also by Torrey and Gray, Lcdebour, and 

 most authors. S. muscoides, AVulff., is the common Middle and S. European form. 



6". sileiiiflora is confined to Arctic America ; and Jilagellanica, in a form identical with 

 exarata, does not extend in S. America north of Peru. 



S. controversa, Sternb., which, according to most authors, is a synonym of adscendens, 

 has been found on the Rocky Mountains by Bourgeau and Hector during Palliser's Expe- 

 dition, but nowhere else in Continental America. 



S. exilis, DO. This, as suggested in ' Elor. Bor.-Am.,' is, so far as may be judged by 

 specimens tallying with the description, certainly only a weedy state of cernua. 



S. bidUfera, L. Koch distinguishes this from granulata by its leafy cyme and other 

 characters that appear to be clearly connected with its being a bulbilliferous condition of 

 S. granulata, between which and bulbifera I find intermediate grades. Ledebour and 

 Eries also keep it distinct. It is not Arctic Lapponian, but Russian. 



S. Ivyperborea, Br., is referred to r'wularis /3 in ' Elor. Bor.-Am.' and by Torrey and Gray ; 

 it is often a starved high-arctic form, but not a permanent or well-marked one ; it is con- 

 fined to Arctic America, and Greenland. 



S. coriacea, Adams. This appears to me, from the description, not to be distinct from 

 nivalis. I have seen no authentically named specimens. 



S. reflexa. Hook. This is certainly only Virginiensis, of which several specimens from 

 the Rocky Mountains precisely accord with the arctic. 



S. hieraciifolia, W. & K., though Arctic Russian, fid. Ledebovir, is not Lapponian, 

 according to Eries. . 



S.foliolosa, Br. This is a monster, as pointed out by Eries {comosa), rather than a 

 variety proper, the foliaceous cyme and bulbilli being produced at the expense of the 

 inflorescence proper. Ledebour reduces it, and Ruprecht notices its transition to stella- 

 ris, L. 



S. propinqua, Br., is identified with Hirculus, L., in 'Elor. Bor.-Am.' and by most suc- 

 ceeding authors. 



