3^8 DR. HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 



specimens from arctic habitats, are to me unavailable characters ; Koch also keeps them 

 distinct, and characterizes them by their leaves. 



E. Uneare, Muhl. Fries keeps this distinct from jpa^H'Stre, L., both being found in 

 Lapland. It is referred io paliistre, var. /3, in the ' Flora Bor.-Am.,' in Torrey and Gray's 

 Flora, and in Asa Gray's Manual. 



Callitriche verna, L. I have treated this as one collective species, including autum- 

 nalis, following Bentham's idea. Fries keeps this and cmtumnalis, L., distinct, giving 

 Lapland as a habitat for both. Bentham unites them. A. Gray and most authors keep 

 them distinct. 



Myriophyllum spicatnm, L., is not Lapponian according to Fries, though Lapland and 

 Asiatic Russia are given as habitats by Ledebour. 



Hippums Montana, Led. I have not seen this plant, which, judging from Ledebour's 

 description, would appear undoubtedly to be only a starved state of H. vulgaris. S. ma- 

 ritima, Hellen, is reduced by Wahlenberg, Fries, and Koch to a variety of vulgaris ; on 

 the other hand, it is retained as a species by Bro^vn, Ruprccht, ' Flor. Bor.-Am.,' and 

 Torrey and Gray. Both this and vulgaris are arctic. 



Ceratophyllum. Owing chiefly to imperfect materials, I am obliged to treat Cerato- 

 jjliyllmn as consisting of one collective species. The specimens I have examined do not 

 present such definite characters in the fruit as the descriptions of authors would seem to 

 imply. Bentham regards siihmersum and demersum as forms of one ; Torrey and Gray 

 suggest that there is but one American species ; Fries, Koch, and Watson keep these two 

 distinct. Neither of them are Arctic European or Asiatic, though found in Arctic 

 America. 



Claytonia lanceolata, Pursh, arctica, Adams, and sarmentosa, C. A. M., are undoubt- 

 edly trifling varieties of one plant, neither constant inter se nor as to locality. 



MoNTiA/oji^cmffl, L. The absence of this cosmopolitan plant in all parts of Temperate 

 America east of the Rocky Mountains, except Labrador, is one of the most remarkable 

 facts in botanical geography. Newfoundland is given as a habitat by Le Pylaie ; but this, 

 like that of Calluna vulgaris, wants confirmation. 31. rivularis, Gmel., is reduced to a 

 variety by Fries and Torrey and Gray. 



Sedum elongatum. Led. I do not know this plant by authentic specimens. Ledebour 

 gives it as a doubtful species, confounded with *S'. Rhodiola by Chamisso, Hooker and 

 Arnott, and Torrey and Gray. 



S. eupliorUoides, Schl. Of this I know nothing; according to Ledebour it is pro- 

 bably a variety of the Siberian S. algidmn, Led., itself very near to quadrifidum. Pall. 



RiBES propinqimm, Richardson. This does not differ from R. ruhrnm, L., to which it 

 is reduced as var. ^ by Trautvetter and Meyer in ' Flora Ochotsk.' 



Chrysosplenium tetrandrum, Lund, is noticed by Fries as a variety of alternifolium, 

 also occurring in Lapland. I have not seen authentic specimens. 



Parnassia obtusijloi'a, Rupr., appears nothing but a small specimen of palustris, L., 



