120 
CnrCIFOK.M PLANTS . 
tanica, the Atropa frutescens, and the arborescent Sonchus, 
vegetate there in the loose sands, and afford, as in Africa, 
food for camels. The western group of the Canaries pre- 
sents a more elevated soil, is more woody, and is watered 
by a greater number of springs. 
Though the whole archipelago contains several plants 
found also in Portugal,* in Spain, at the Azores, and in the 
north-west of Africa, yet a great number of species, and 
even some genera, are peculiar to Teneriffe, to Porto Santo, 
and to Madeira. Such are the Mocanera, the Plocama, the 
Bosea, the Canarinn, the Drusa, and the Pittosporum. A 
form which may be called northern, that of the cruciform 
plant, f is much rarer in the Canaries than in Spain and in 
Greece. Still farther to the south, in the equinoctial regions 
of both continents, where the mean temperature of the air 
rises above twenty-two degrees, the cruciform plants are 
scarcely ever to bo seen. 
A question highly interesting to the history of the pro- 
gressive marks of organization on the globe has been very 
warmly discussed in our own times, that of ascertainin'^ 
whether the polymorphous plants are more common in the 
volcanic islands. The vegetation of Teneriffe is unfavourable 
to the hypothesis that nature in new countries is but little 
subject to permanent forms, hi. Broussonnet, who resided 
so long at the Canaries, asserts that the variable plants are 
not more common there than in the south of Europe. May 
* M. Willilenow and myself found, among the plants of the peak of 
Teneriffe, the beautiful Sutyrium diphyllum (Orchis cordata, Willd.), 
which Mr. Link discovered in Portugal. The Canaries have, in common 
with the Flora of the Azores, not the Dicksorsia culcita, the only 
arborescent heath found at the thirty-ninth degree of latitude, but the 
Asplenium palmatum, and the Myrica Faya. This last tree is met witli in 
Portugal, in a wild state. Count HofTmansegg has seen very old trunks 
of it; hut it was doubtful whether it was indigenous, or imported into 
that part of our continent. In reflecting on the migrations of plants, and 
on the geological possibility, that lands sunk in the ocean may have 
heretofore united Portugal, the Azores, the Canaries, and the chain ol 
Atlas, we conceive, that the existence of the Myrica Faya in western 
Europe is a phenomenon at least as striking as that of the pine of Aleppo 
would be at the Azores. 
f Among the small number of cruciform species contained in the 
Flora of Teneriffe, we shall here mention Cheiranthus longifolius, I’Hdrit. ; 
Ch. fructescens, Vent.; Ch. scoparins, Brouss. ; Erysimum bicornc, Aiton; 
Crambe strigosa, apd C. lsevigata, Brouss. 
