1917.] 



THE FLORA OF THE SWISS ALPS 



41 



alpine types restricted to the Alpine range and the Carpathian 

 Mountains; they are near relations of the great Rhododendrons of 

 the Himalaya. They ascend to 7,000 feet; it is very probable that 

 their upper limit is an indication of the former upper limit of trees. 

 Also the green Alder (Alnus viridis (Chaix) Lam.) covers the 

 slopes immediately under and above the actual tree-line with its 

 bright green, helping to fasten slipping ground. 



Fig. 17. The Dwarf Pine (Pinus montana Mill. var. prostrata Tu- 

 beuf) covering a grassy slope near Davos; about 2,000 meters above 

 the sea. Photo Wiinsche. 



The dwarf Pine (Pinus montana Mill. var. prostrata Tubeuf) 

 (Fig. 17) ranks especially as a pioneer on calcareous slopes; the 

 black masses assaulting the fortresses of moving rubbles in the dolo- 

 mites of the lower Engadine consist of dwarf pines. With its long 

 flexible twigs, this bush is marvelously adapted to retard avalanches 

 and to protect the soil. These larger shrubs of the shrub-belt are sub- 

 stituted in higher altitudes by stunted little dwarfs, which spread 

 over the ground with horizontal twigs, all in one level like a mat. 



A near relation of the Rhododendrons is the trailing Azalea 

 (Loiseleuria procumbens (L.) Desv.), which forms a thick carpet 

 on the ground and opens its beautiful little rose-flowers in the be- 

 ginning of the alpine spring. It has a wide distribution ; it is a domi- 

 nant type in the circumpolar tundra, lives in the Altai, the Pyre- 

 nees, the Alps, Carpathian and Balkan mountains. But notwith- 

 standing this wide spreading it has no varieties and is the only spe- 



