BOTANICAL GEOGRAPHY. 447 



Salsola, and Juncus acutus. The following are among the endemic forms of 

 the second region of Granada, in addition to those already mentioned, e. g. 

 Aplectrocapnos bcetica, Crambe filiformis, Hypericum bteticum and caprifolmm t 

 Rhammts velntinus, Ulex baeticus, Genista biflora and Haenseleri, Sarothamnm 

 affinis, Ononis speciosa, Anthyllis tejedensis, Saxifraga gemmulosa, Mtsoselinum 

 millefolium, Lonicera splendida, Santolina canescens, viscosa, and pectinata, 

 Centaurea acaulis, Clementei, prolongi, and granatensis, Cynara alba, Cha- 

 mapeuce hispanica, Digitalis laciniata, Salvia candelabrum, Thymus longi- 

 florus, Teucrium fragile and Eaenseleri, Salsola Webbii and genistoides, 

 Euphorbia Clementei and leucotricha, and Oligomeris glaucescens. 



Third region (Bossier's alpine region), from 4500' (5000 X ) to 8000'. The 

 name applied to this region is not fortunately selected, because at the most 

 it could only be compared with that of the subalpine vegetation of the 

 Alps. But considering that, in addition to many endemic plants, at least a 

 large proportion (two fifths) consist of the plants of Central Europe, it would 

 have been more appropriate to have named it after them. But the question 

 of whether the region possesses natural boundaries is of more importance 

 than that regarding the name. On this point it is at once evident, that the 

 tree-limit, which in most mountains so sharply defines the Central European 

 from the alpine region, coincides in the present instance with the latter 

 (6000' to 7000') according to Boissier's estimation. Among the trees which 

 vegetate here we have Pinus sylvestris, Taxus, Saliao caprea, and Sorbus 

 Aria ; hence, in fact, forms belonging to the forests of Central Europe. 

 Now if, as in the Sierra Nevada, the forests had diminished to such an extent, 

 or in the course of time had disappeared, so as at the present day not to have 

 any considerable influence upon the natural character of the mountains, still, 

 to allow of comparison with other mountains, it is requisite to determine the 

 regions according to the sphere of distribution of those species which inhabit 

 a large portion of Europe, and thus afford the most certain standard for the 

 climate of any particular region. In the distribution of a mountain into 

 regions, the height at which the vegetation undergoes a decided change is 

 not the only point to be taken into consideration, but also where the climates 

 corresponding to those of other latitudes approximatively occur ; a determi- 

 nation which can only be made by the comparison of the vertical distribution 

 of the same plants. There is another decided reason, which renders it 

 essential to form the regions of the Sierra Nevada beyond the tree-limit (part 

 of Boissier's alpine region and his snow-region) into one. Boissier does not 

 give any other decided difference between the two, than that in the snow- 

 region flakes of snow remain during the summer, and that the taller shrubs 

 are absent. That as the altitude increases, the alpine plants themselves 

 alter considerably, is always found to be the case in the upper mountainous 

 regions ; hence the latter might be subdivided, without the accuracy and 

 distinctness of the representation being increased. But the region of 



