DR. HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 315 
this plant, in which state it differs in no respect from pratemis. I have not seen the 
fruit, however. 
C. umbrosa, DC, is referred by Fries to a variety of amor a, L. ; both are Lapponian. 
Eutrema arenicola, Hook. I have examined this plant very carefully ; it is certainly 
not a Eutrema. In the few specimens known to me the radicle is slightly oblique. 
Turczaninoff (in Herb. Hook.) suspects that it may be his E. pWferum {Draba grand* 
flora, C. A. M. ; Pachyneurum grand Iflor urn, Bunge ; Bray a Meyeri, Bge. ; Parr a* mi- 
crocarpa, Led.) ; but I find no traces of the peculiar hairs of this plant in the P. arenicola. 
Richardson observes that it ranges from 107°-150° W. I have seen no specimens but his 
own. 
i 
Vesicaria arctica, Rich. Planchon, who has examined the specimens in the Hookerian 
Herbarium with a great deal of care, confirms the identification of the Chilian j 
the arctic. It is singular that this plant should be found as far north as 81° in Green- 
land, but not amongst the Polar American Islands. 
Draba. Of all the arctic genera, none but Salix present so many difficulties as Draba. 
Whether by variation, or hybridization, or other unknown cause, the prevalent forms seem, 
wherever they grow, to pass into one another by insensible gradations ; and no botanist 
has succeeded in bringing the arctic stunted varieties within such specific limits as to haw 
gained the assent of others. No doubt many are, in their arrested condition of growth, 
absolutely un distinguishable in the present state of science ; and whoever attempts their 
discrimination must expect to change his opinion somewhat at every re-examination. 1 
am fortunate in having Mr. Ball's advice upon some of the European species, which he 
has studied with great care, and have followed his opinion in the naming and groupim 
the arctic ones ; unfortunately, however, he has not completed his study of the genus, 
nor of all the species here enumerated ; so that the geographical data are approximate 
only ; nor does he speak with implicit confidence of their synonymy. In addition to the 
excellent critical notes he has published in the Bulletin of the Botanical Society of Paris 
(vol. vii. pp. 227 & 247), I have from him the following provisional grouping of the com- 
moner forms : 
1. B. androsacea, Wahl., 1812, an Willd 
D. Wahlenbergii, Hartm. 1820. D. Lappon 
2. D. Flactuitzensis, Wulf., Jacq. Misc. 
D. lactea, Adams. ? D. Carinthiaca, Hoppc 
3. B. miiricella, Wahl. 
D. nivalis, Lilj., non DC. 
4. B. rupestris, Br. 
D. AUaica, Bge. 
5. B. hirta, L. 
D. Dovrensis, Fr. D. arctica. Vahl. 
6. B. incana, L. 
D. contorta, Ehr. D. confusa, Ehr. & DC. D. Thomasii, Koch. 
VOL. XXIII. 2 U 
Willd. ? D. nivalis, DC, non Lilj. 
ifolia 
