488 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1963 



Phanerophytes and hemicryptophytes are the two largest classes in 

 the world's flora as a whole; (2) warm humid regions have a pre- 

 ponderance of phanerophytes; (3) warm arid regions are overly 

 represented by therophytes; and (4) chamaephytes predominate in 

 arctic and alpine regions. This last generalization is significant to 

 our discussion here. 



Cautiously applied, Kaunkiaer's scheme provides one means of quan- 

 tifying the physiognomy of vegetation. It also serves in this case to 

 focus our attention on several adaptive features of arctic-alpine plants 

 in general. Perennating buds simply could not survive the freezing 

 and desiccating arctic and alpine winds without heavy protection ; and 

 one would expect the environment to select in favor of those species 

 and biotypes that have their renewing buds at or near the surface of the 

 ground — in other words, low chamaephytes and hemicryptophytes. 

 Maximum protection from the environment, harsh both above and 

 below ground, is provided at the surface by the litter and snow. These 

 are precisely the classes, of course, that Kaunkiaer's scheme shows to be 

 most abundant in the Arctic. Good examples of very low chamae- 

 phytes are the dwarf willows, purple saxifrage, and mountain avens 

 (pis. 5, 9) ; their perennating buds are scarcely over an inch or two 

 above the ground in winter. The bilberry or arctic blueberry (pi. 8) 

 can be either a tall chamaephyte or short phanerophyte. Numerous 

 herbs that die back to the ground completely each year or form basal 

 rosettes fit the category of hemicryptophyte, although the distinction 

 between this class and chamaephytes is in cases debatable as indeed be- 

 tween all the classes. The lines are arbitrary and for convenience only. 

 A large flora of geophytes is precluded in the Arctic by permafrost. 



It is common knowledge that the floras of high latitudes and high 

 altitudes are comprised predominantly of perennial species. Owing 

 to the extremely vigorous and selective environment, establishment by 

 seed or other propagule is a very difficult and fortuitous event at best. 

 Consequently, it is of supreme advantage to a species or biotype if once 

 it gets a foothold it is able to colonize rapidly and endure for more 

 than a single season. Perennials clearly have the edge on annuals, and 

 the northernmost floras have few if any annual species. The abun- 

 dance of grasses and sedges in tundra vegetation is particularly note- 

 worthy in this respect. A species may not always have the same 

 duration in every habitat, however. The European Linaria alpina 

 Mill, (toadflax), for example, is annual in the lowlands, biennial in 

 the lower mountains, and perennial at high altitudes. Low tempera- 

 tures seem to reduce the annual duration of vegetative growth while 

 increasing the life-span of the individual (Combes, p. 100). 



There is a vast literature on the subject of plant communities in the 

 Arctic- Alpine environment, and it would be foolish for me to attempt 

 either summary or synthesis here. Particularly noteworthy, insofar 



I 



