Geographical Distribution of the Cruciferce. 11 



ness of the Cakilc in a dry sand, where most other plants of the 

 same order would have withered and perished. 



In taking leave of this most useful and interesting order, I may 

 with propriety quote from Sir John Richardson's very able obser- 

 vations at the end of his "Journal of a Boat Voyage," published 

 in 1851. Regarding Polar plants, he says : — " Of the Polar 

 " plants, amounting to 91 species, which inhabit Melville Island, 

 " the shore of Barrow's Straits to Lancaster's Sound, and the 

 " north coast of Greenland, between the 73rd and 75th parallels 

 " of latitude, about |ths range to Greenland, Lapland, or Northern 

 " Asia. Of the remainder some have been gathered on the shores 

 " of the Arctic Sea from Baffin's Bay to Behring's Strait-, and it 

 " is probable if these high latitudes were fully explored, the Flora 

 " of the entire zone would be found to be uniform. Some of the 

 "more local plants will perhaps be ascertained, on farther ac- 

 " quaintance, to be mere varieties altered by peculiarities of 

 " climate. That the Flora as well as the Fauna of the high 

 " northern latitudes is nearly alike in the several meridians of 

 " Europe, Asia and America, has long been known ; and even 

 " when to some distance south of the Arctic circle, we find that 

 " this law is superior to the intrusion of high mountain chains, 

 " and is but partially infringed upon." Further on he observes : 

 " The families of Polar plants which are most rich in .ire 



" the Cruciferae, Gramineae, Saxifrageae, Caryophylleae and Com- 

 " posits. Of these, the Saxifrageae are most characteristic of 

 " extreme northern vegetation. All of them that inhabit the 74th 

 " parallel in America are found also in Spitzbergen, Lapland or 

 "Siberia; and even the Polar species are twice as numerous as 

 " those which exist in the wide district which ' Gray's Flora of 

 " the Northern States' comprehends; and we may add, that the 

 "plant which Humboldt traced highest in the Andes, was a 

 " Saxifrage. The Caryophylleae and Cruciferae, which vie with 

 " the Saxifrageae in number on the 74th parallel, include many of 

 " the doubtful species above alluded to." 



There is no doubt every reason to believe that Sir John's words 

 as to the unlucky multiplication of species through the separation 

 of varieties will some time or other prove true, not only in the 

 plants of the Arctic zone, but also in those further south. More 

 extended acquaintance with both will correct our knowledge in 

 that particular. Able monographs amongst American and Euro- 

 pean botanists will do this work, so much required. 



