314 DR, HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 
treat the distribution of vulgaris, Br., stricta, Andrz., and arcuata Reich., in connexion. A. 
Gray considers the American stricta and arcuata as varieties of vulgaris. Bentham says that 
B. vulgaris, pracox, and stricta pass through every gradation into one another. Another 
element of confusion in this group is the doubtful origin of the common pot-herb B. prce- 
cox. Watson treats it as an alien. Torrey and Gray, on the other hand, describe it as a 
native of Canada, ascending to 68° N., though perhaps stricta is here meant, for A. Gray 
latterly refers prcecox of PI. Bor.-Am. to vulga 
and rightly as far as the 
specimens I have examined go to show. Tries remarks (Summ'a, p. 146) that Smith's 
original prcecox (Flora Britannica) is a cultivated arcuata, the English Botany plant being 
different (thus accounting for Nyman's conclusions above stated). My North Indian and 
Himalayan Barbareas are, again, generally referable to the European forms, though 
scarcely characteristic of them. I long endeavoured to keep the Australian and New 
Zealand form distinct ; but neither Bentham nor Mueller regard it as different from vuU 
garis, with which undoubted wild specimens from the Australian Alps well accord. 
Turuitis patula, Graham, and retrofracta, Hook., are, I think, identical with T. mollis, 
Hook. The Arabis Holbollii, Horn., is another synonym. There are certainly differences 
in the length and breadth of the pod in both patula and retrofracta ; but these do not at 
all indicate the seeds being in one or two rows, which is a very variable character in both. 
Arabis Holbollii is identified with A. retrofracta, Grah., by Lange. 
Arabis lyrata, DC. This, which is the Sisymbrium humifusum, J. Vahl, and Arabis 
sisymbrioides, Hook., differs according to descriptions from A.petrcea, Lamk., in the rather 
oblique radicle of the embryo, and biennial root (Torrey and Gray, i. 80, 81), neither of 
which characters appear to me to hold good in the rather numerous specimens I have 
examined, the radicle being in both variable as to direction, and the roots identical. In 
habit and every other respect, the plants entirely accord, as far as herbarium specimens 
allow me to judge. According to Fries, A. petrcea is not a native of Lapland; nor does 
Ledebour give any European or Asiatic arctic habitat for it ; it is, however, common in 
Finland, Scandinavia, Iceland, and N. Britain. Fries includes A. ambigua, DC under 
it, a plant kept distinct by Ledebour and by Torrey and Gray. 
Cakdamixe bellidifolia , L. I have sometimes been almost disposed to suspect that 
this may be an arctic form of hirsuta, to which it certainly is very closely allied, and to 
which it tends through microphylla, Willd. C. Lenensis is identical with bellidifolia, and 
is var. Lenensis, Trautv. (Florula Taimyr.). 
C. hirsuta, L. This, though a common Icelandic plant, and one that crosses the circle 
m America, does not occur in Scandinavia north of Gothland and Finland. The C. sy ha- 
tha, Link, is distinguished by its six stamens, spreading pedicels, and style as long as the 
siliqua is broad,— all variable characters, except that of the stamens. In the southern 
hemisphere and elsewhere C. hirsuta is hexandrous. Watson finds no difiiculty in distin- 
guishing these as wild plants in England, but considers sylvatica a doubtful species, 
adding that the distinctions are less decided under cultivation. Bentham considers sylva- 
tica to be a large luxuriant hexandrous form of hirsuta. 
C. digitata, Eich. I have examined a large suite of excellent flowering specimens of 
