28o Eduard Riibel 



feel carried back to the glacial period. What interesting prob- 

 lems wait here for study! If the Alps in the glacial age had a 

 climate similar to that of western Washington today (the glacial 

 age snow limit of the Wallis coincides with Washington's of 

 today), the greater part of the Alpine flora may have survived. 

 The country north of Washington and into Alaska would 

 surely give still better parallels. A study of this vegetation in 

 respect to these questions of ecologic dependencies is ardently 

 desired, nay, even demanded! 



7 J. Aciculifruticeta: Needle-leaved scrub. — These unpretend- 

 ing communities occur where more pretentious ones give way : 

 in the mountains near the tree limit, and lower down when 

 edaphically the conditions are less favorable, as on desolate 

 calcareous slopes and badly aerated raw humus soils. The best 

 known is the dwarf-pine scrub (Pinus mugo), which covers 

 much area in the Alps, partly edaphically, in larger part biot- 

 ically enlarged by forest-felling in former times. 



i^.Duriherbosa: Hard grass prairie. — Duriherbosa are grass- 

 lands in which the dominant species have vegetative organs 

 more strengthened by the development of the mechanical tissue 

 than by turgescence, and which die down in winter. The climate 

 is fairly continental with dry periods (semiarid to semihumid). 

 Essential is the seasonal repetition of the precipitation; there 

 are early summer rains just at the vegetative season, which en- 

 courage the growth of a grass sward. Two groups are to be 

 distinguished — one winter-cold, the other warm (savannah); 

 in common are the deciding dryness and the summer rains. 



Hungarian and southern Russian sward steppes are conspicu- 

 ous, called "pussta" in Hungary, "black earth steppes" in Russia. 

 Dominant grasses are Stipa capillata and St. pennata, Andro- 

 pogon gryllus, and, on the best black earth, Festuca vallesiaca 



