OCR Text |
Show ANNOTATIONS AND ADDITIONS. 325 istic form of the species of Erica, including Calluna (Erica) Vulgaris, L., the common heather. "While, in Europe, Erica carnea, E. tetralix, E. cinerea, and Calluna vulgaris, cover large tracts of ground from the plains of Germany, France, and England, to the extremity of Norway, South Africa offers the most varied assemblage of species. Only one species which is indigenous in the Southern Hemisphere at the Cape of Good Hope, Erica umbellata, i::: found in the Northern Hemisphere, i. e. in the north of Africa, in Spain, and Portugal. Erica vagans and E. arborea also belong to the two opposite coasts of the Mediterranean : the first is found in North :Africa, near Marseilles, in Sicily, Dalmatia, and even in England; the second in Spain, Italy, !stria, and in the Canaries." (Klotzsch on the Geographical Distribution of species of Erica with persistent corollas, MSS.) The common heather, Call una vulgaris, is a social plant covering large tracts from the mouth of the Scheidt to the western declivity of the Ural. Beyond the Ural, oaks and heaths cease together : both are entirely wanting in the whole of Northern Asia, and through$ut Siberia to the shores of the Pacific Ocean. Gmelin (Flora Sibirica, t. iv. p. 129) and Pallas (Flora Rossica, t. i. pars 2, p. 53) hav-e expressed their astonishment at this disappearance of the Calluna vulgaris-a disappearance which, on the eastern declivity of the Ural Mountains, is even more sudden and decided than might be inferred from the expressions of the lastnamed great naturalist. Pallas says merely: "Ultra Uralense jugum sensim deficit, vix in Isetensibus campis rarissime apparet, et ulteriori Sibirire plane deest." Chamisso, Adolph Erman, and Heinrich Kittlitz, have found Andromedas indeed in Kamtschatka, and on the north-west coast of America, but no Calluna. The accurate knowledge which we now possess of the mean temperature of several parts of Northern Asia, as well as of the distribution of the annual temperature into the different seasons of the year, affords no sort of explanation of the cessation of heather to the east of the Ural Mountains. Joseph Hooker, in a note to his Flora Antarctica, has treated and contrasted with great sagacity and clearness two very different phenomena which the distribution of plants presents to us: on the one hand, "uniformity of surface accompanied by a similarity 28 |