VEGETATION OF CONGLOMERATE ROCKS 



385 



ill number, one dominated by crustose lichens, the other by 

 fohose Uchens. 



The first or crustose hchen stage is seen on the smoother and 

 more exposed rock faces. The patches of crustose hchens are 

 separated by spaces of bare rock, or rarely nearly cover the 

 surface. The lichens most commonly found are Lecidea sp., 

 Pertusaria communis, Staurothele umbrina, Verrucaria muralis, 



Fig, 2. The foliose lichen, Dermatocarpon miniatum, on steep rock surface 

 facing 825° W; scattered herbaceous plants in pockets. Both transects, figures 

 4 and 5, cross this area. 



and Placodium citrinum. With these crustose lichens, but of 

 only minor importance in this lichen community, is the xero- 

 phytic moss, Grimmia apocarpa. Foliose lichens begin to ap- 

 pear early in the crustose lichen stage, but reach their cul- 

 mination only on partially shaded rocks. 



The second or foliose lichen stage is dominated by Dermato- 

 carpon miniatum. Where best developed the large gray thalli 

 of this plant nearly cover the rock surface (fig. 2). A few 



