388 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1950 



tained fragments of calcium carbonate and green algal cells, while 

 the hyphae and dead algal cells were apparently digested. Experi- 

 ments have sliown that snails will feed on potatoes covered with 

 cetraric, rhizocarpic, and pinastrinic acids, poisonous to other ani- 

 mals, but will not feed on vulpinic acid, which is recognized as poison- 

 ous to vertebrates. Bitter-tasting lichens, treated by a soda method 

 to extract the acids, were acceptable in preference to fresh untreated 

 but moistened lichens. This is of interest, since there is a widely cur- 

 rent assumption that lichens are remarkably well protected against 

 attacks from animals by reason of these acids. 



Free-living algae are the preferred foods of invertebrates, in most 

 cases, but when not obtainable, the gonidia, i. e., the algal layers in the 

 lichen thallus, are taken. Some lichens are normally scarred from 

 snail feeding ; UmhilicaTia mammulata^ common to the eastern United 

 States, is frequently seen with the dorsal surface marred. Hue (13)' 

 presented the opinion that the abundance of lichens in Arctic regions 

 results from the comparative absence there of snails and insects. 

 Not a few "new"' species of lichens have been the result of insect and 

 snail ravages, further modified by plant regeneration. 



LICHENS USED AS FODDER 



Nongrassy ranges. — This subtitle refers specifically to range lands 

 which are composed primarily of lichens or which are used at definite 

 times of the year for grazing because of the lichen vegetation. Such 

 areas are rarely entirely free of sedges, grasses, herbaceous plants, low 

 bushes, and sphagnum bogs. When this type of vegetation is at its 

 best in spring and summer, it has little value as nongrassy range land. 

 These areas lie north of the tree line and above timber line but may 

 extend well down into the timber along mountainsides. They are 

 best developed in sub-Arctic regions but may extend into the temper- 

 ate zones. They cover those parts of Greenland which are ice-free 

 and still have sufficient moisture for plant growth, Iceland, northern 

 Scandinavia, Siberia, Alaska, the Northwest Territories of Canada, 

 Labrador, and the archipelago of the Arctic Sea. As a whole, the 

 thousands of square miles composing this area furnish nongrassy 

 range feed in the winter for wood buffalo, musk ox, caribou, and other 

 wild herbivores, and for domesticated reindeer, as well as a grassy 

 range feed at all other times. It is not to be assumed from this state- 

 ment that all these wild species of animals are entirely dependent on 

 lichen forage for winter grazing. Actually, too little is known of 

 their food preferences to permit a definite statement. 



In the Antarctic regions, though lichens are the predominant plants, 

 they are not so richly developed as in the Arctic. Owing to absence 



« citations not recorded In the bibliography of this article may be found In the author's 1944 paper (13) 



