Rydberg: Phytogeographical notes 93 



but not so common in the Alps. It is the only species of the 

 group there. It is, therefore, not probable that its ancestry came 

 from that region. The group is represented in both North 

 America and Asia by several species. The American species, 

 except P. nivea and P. uniflora, are rather local, and are modified 

 to adapt themselves to local conditions. Both P. nivea and P. 

 uniflora as well as P. villosa (found in the northwestern corner of 

 this continent) are found in Asia, together with several others of 

 the group. P. nivea itself is common there in the mountains as 

 well as in the arctic, while it has been collected only at a few 

 places in the Rockies of Colorado. It is therefore probable that 

 the group originated in Asia. 



Let us now discuss the plants of this category. The following 

 plants are common to the arctic regions of both continents, the 

 Alps, and the Rockies as far south as Colorado. Most of these are 

 also found in Asia. Those with a star are also found in the 

 subalpine regions. 



*Phleum alpinum Salix reticulata 



*Trisetitm subspicatum Oxyria digyna 



*Deschampsia caespitosa *Bistorta vivipara 



Poa cenisia Silene acaulis 



*Poa alpina Thalictrum alpinum 



Festuca supina Ranunculus pygmaeus 



* Fes ticca ovina Draba fladnizensis 



*Festuca rubra Muscaria adscendens 



Juncus triglumis Potentilla nivea 



J uncus castaneus * Astragalus alpinus 



*Juncoides spicatum Campanula uniflora 



Lloydia serotina Myosotis alpestris 



Some of these species extend into mountains situated so far 

 south that they could not have been connected with the arctic 

 regions even in the glacial times. The existence of these species 

 there has to be explained in some other way. In most cases their 

 seeds were probably carried by birds or other animals or by 

 the wind. Included among such plants are the following: 



Lloydia serotina, a typical arctic-alpine plant, is found not 

 only in the arctic regions, the mountains of northern Europe and 

 Asia, the Alps, the Rockies and the Sierra Nevada, but also in 



