Botanical Geography of Southern Europe. 305 



we have made a good choice, we must remain long in a country 

 to be enabled to determine the limits of the distribution of a 

 plant. 



It is well known that many, not all, plants of the northern 

 plain occur also on the mountains in the south ; and although 

 such plants are very convenient for marking the relations of the 

 climate of the mountains, yet they are not so well suited for the 

 determination of the relations of the climate of the plains from 

 which we started. These plants also ascend the mountains gra- 

 dually, and do not make wonderful leaps like the buck-thorn 

 (Hippophde Rhamnoides), which the traveller from the island 

 of Riigen to Geneva will not meet with any where else but at 

 these two points. It is fortunate also when the characteristic 

 plant is universally known, so that minute botanical knowledge 

 may not be required for making the desired determinations. A 

 plant well adapted for determining the elevation of the ground 

 is the bilberry or whortleberry (Vaccinium myrtillus). It grows 

 in northern Germany, also near Berlin, in the wooded parts of 

 the plains. It then gradually ascends : occurs near Freyburg 

 in Baden, but only on the higher mountains ; in Switzerland it 

 grows in the woods of the lower Alps, then reappears for the 

 first time on the high Alpe di CaporagJteno, above Fivizzano, 

 where it flourishes in the meadows along with the Cokhicum 

 autumnale. There it was also met with by my friend the late 

 Professor Hoffman, shortly after my visit to the place. Finally, 

 it is afterwards to be sought for only on the high Majella, in 

 the Abruzzi. 



Let us return to the plains, and afterwards consider the lines of 

 separation of the plants of Southern Europe. After we have com- 

 pletely left the Alps, there very soon makes its appearance a uni- 

 versally known plant, the lavender (Lavandula spica). It occurs 

 on the sunny hills around Verona ; it is particularly abundant be- 

 hind Coni, towards the Col di Tenda, constantly following the 

 mountain chain; then extends to the south of France and Spain, 

 and is still abundant in Aragon, but further in the interior and in 

 the plains of Castile it is not found ; and it is no where met with 

 in Portugal. It. also ceases in the direction towards Rome, and 

 only makes its appearance among the high mountains which 



