490 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1963 



flushes and snowpatch areas. Typical examples of tundra prairie are 

 illustrated by the pictures in plates 3 and 10, taken in the Alaskan Arc- 

 tic. One was taken before most species had begun to flower and the 

 other at the peak of flowering. The cottongrass tussock meadow (pi. 

 10), often called "niggerhead" meadow, is one of the most characteris- 

 tic plant communities of the Arctic. The principal tussock- forming 

 species is the sedge Eriophorum vaginatum L. (cottongrass), a 

 strongly cespitose (clump-forming) species. By a combination proc- 

 ess of their own growing habit and the perennial forces of freeze and 

 thaw, these sedges build up over a period of years more or less conical 

 momids, composed primarily of organic remains of previous growth. 

 The new year's growth is always at the apex of the tussock. Other 

 plants, not able to thrive in the wetter depressions, can often gain a 

 foothold on these relatively dry tussocks. The top of the mound, ex- 

 cluding the new stems, may be a foot or more above the surrounding 

 depressions. Only those who have tried to hike for miles across these 

 niggerhead meadows can fully appreciate just what sort of landscape 

 the tussocks create. In total aspect, these meadows are very attractive 

 when the "cotton" (fruiting-head bristles) is ripe; from the air one 

 sees this cotton dominating the landscape for hundreds of miles along 

 the Alaskan Arctic Slope for several weeks, looking just like a light 

 fresh snow. 



Arctic freshwater habitats are generally quite sterile because of the 

 frigid water temperatures, even in summer, and the presence of ice 

 through much of the year. Shallower lakes and streams freeze to 

 the bottom in winter, and the deepest lakes may be so cold year- 

 round that they scarcely lose their surface layer of ice before a new 

 layer begins to form. Nonetheless, a fair number of aquatic species 

 do recur across the Tundra in lakes, ponds, and streams. Pondweeds 

 {Potamogeton spp.), several species of buttercups {Ranunculus spp. 

 and Caltha spp.), and marestail {Hippuris vulgaris L.) are some of 

 the most widely occurring ones. 



MORPHOLOGICAL CHARACTERISTICS OF ARCTIC-ALPINE PLANTS 



One could accumulate from the literature a fairly long catalog of 

 specific correlations of morphological features with environmental 

 factors, demonstrated for this or that species or taxonomic group, but 

 precious few generalizations can be made about arctic- alpine plants 

 as a whole. For example, I can demonstrate statistical correlations 

 between height of plant or diameter of corolla and altitude in 

 Campanula rotundifolia L., the harebells, an extremely polymorphic 

 complex on which I have done considerable research. Height 

 decreases as altitude increases, a negative correlation, and corolla 

 diameter increases while altitude increases, a positive correlation. To 

 a degree, but harder to show statistically, these same correlations exist 



