REINDEKK (!UA/I.\G INVESTIGATIONS IN ALASKA 



23 



Tho species of Cetnn 'in ami Stereocaufoii aie al^o iiiip.ortant but 

 ]ess abundant. Browse and dried lierbaceous ve<!;etation are taken 

 to some extent and occasionally some of the mosses. 



THE LICHEN PLANT 



The plant.*? tliat furnish the bulk of the forag-e on winter ran^e 

 are lichens. They are entirely dill'erent fi'om hei'baceous and shrub 

 ve<>etation in character and in reaction to grazing use. They do 

 not, like the herbaceous vegetation, furnish a renewed forage crop 

 from year to year, but recpiire a long period of years to recover 

 from one season's cropping. Lichens grow very slowly and are of 

 limited height, but attain a very gi'eat age. They are of com- 

 j)aratively delicate structure, infirmly anchored to the soil, and are 

 readily ivmoved either by trampling or picking by hand. Under 

 sunnner conditions they often become dry and brittle and are then 

 easily destroyed. When moist or wet they are of almost spongy 

 texture and then less easily injured. 



The lichen plant is a composite organism — an alga and a fungus 

 living together. The relationship has become so intimate that 

 lichens are often regarded as autonomies or morphological units 

 i-ather than symbiotic colonies of algae and and fungi. The frutili- 

 cation of the lichen is that of the fungus, and reproduction takes 

 l)lace by means of the spore. Many lichens also nudtiply asexually 

 by means of soredia, produced by the chlorophyll-bearing cells, go- 

 nidia, which belong to the algae, the soredia escaping from the 

 lichen thallus usually in the form of a fine powder, and germinating 

 innnediately to form new plants. A third mode of reproduction is 

 by the distribution of fragments of the plants by action of wintl or 

 animals, 



GROWTH HABITS OF LICHENS 



Lichens grow under a great variety of conditions of climate and 

 habitat. (Pis. VI and 13.) Their general distribution both verti- 

 cally and horizontally is extensive. All are capable of enduring 

 desiccation for long periods without losing their vitality. Their 

 height is limited, but the size to which they may attain varies with 

 individual species and habitat. Along the Alaskan coast, the aver- 

 age growth of the mixed stand is 4 or 5 inches, although in places a 

 lO-incli height has been found (pi. 13, fig. 2). Some s})ecies are of 

 diminutive size and consequently of little or no luse for grazing; 

 others are of luxuriant growth and highly valuable. 



Lichens grow chiefly on soil, on rocks or stones, and on the 

 bark of trees; but they also grow frequently on decayed logs and 

 on mosses, and sometimes on the thalli of other species. According 

 to the base upon which they grow they are classified as terricoline 

 (on soil), corticoline (on bark), saxicoline (on rocks), and musci- 

 coline (on mosses). Those most important for forage in Alaska are 

 largely of terricoline habit. The essentially saxicoline, muscicoline, 

 and corticoline species, with a few exceptions, are mostly of diminu- 

 tive size or of low form adhering closely to the substratum, and 

 therefore of low grazing value. 



