DISTRIBUTION IN DIFFERENT PARTS OF THE GLOBE. 571 



in the British flora to the west of Ireland, have the nearest portion of 

 their specific centres in the north-west of Spain; others, confined with 

 us to the south-west promontory of England, are, beyond our shores, 

 found in the Channel Isles and the opposite coast of France ; the vege- 

 tation of the south-east of England is that of the opposite part of the 

 continent ; and the Alpine vegetation of "Wales and the Scotch High- 

 lands is intimately related to that of the Norwegian Alps. The great 

 mass of the British flora has its most intimate relations with that of 

 Germany. He believes, therefore, that these isolated outposts were 

 formerly connected together by chains of land, and that they have 

 been separated by certain geological convulsions. Islands may be 

 considered as the remains of mountain chains, part of the flora of which 

 they still exhibit, and the further they are from continents, the more 

 likely are the plants to be peculiar. 



1 147. All the vegetable productions of the globe are distributed 

 according to harmonious laws, which are by no means fully developed. 

 The greater number of families is distributed over the whole globe ; 

 individual representatives of the groups appearing in different regions. 

 The regions of the globe, as regards their vegetable productions, are 

 related either in the families, the genera, or the species of plants 

 which they produce. By families, Hinds remarks, the most distant or 

 general resemblances are established, constituting analogy. One family 

 may occupy the place of another in certain regions. Thus, the Me- 

 sembryacese of South Africa are represented in America by Cactaceae ; 

 and hi the south of Europe, only by a few species of Sernpervivum and 

 Sedum. By genera, a closer approximation is established that of 

 affinity. The Cistuses of Spam and Portugal are represented by the 

 Helianthemum of the north of Europe ; and the genera of Abies and 

 Pinus, in arctic and temperate regions, have their representatives in 

 the genera Araucaria, Ephedra, and Dammara of the south. By 

 species again, the most perfect accordance of characters or identity is 

 established. 



1148. Meyen states, that the species of a genus, and genera, and 

 natural orders, proceed from a point, and range themselves round it in 

 concentric circles, or spread out from it like rays in all directions ; or 

 are distributed in belts of greater or less breadth, which are parallel to 

 the meridians, or to the parallels of latitude. A genus or family pre- 

 dominates hi certain regions, and attains its maximum there, while in 

 others it is at its minimum. Hence, regions are distinguished by the 

 names of plants which attain their maximum there. Palmae, Mu- 

 sacese, Piperaceaj, and Scitamineae, attain their maximum in the torrid 

 zone, although representatives of them extend to high latitudes, or to 

 the temperate zone. Thus, the Palm called Chamajrops humilis is 

 found in 49 north latitude. The Ericaceae of the old world have their 

 maximum in the south of Africa. A single form, Calluna vulgaris, 



