400 George E. Nichols, 



spruce heath ; but more commonly it represents a primitive 

 phase. Characteristic plants here, in addition to those already 

 specifically mentioned, are the following: 



Lichens 



Cladonia alpestris Cladonia rangifernia 



Cladonia coccifcra Cladonia sylvatica 



Cladonia crispata Cetraria islandica 



Cladonia pyxidata Sphaeophorus coraUoides Pers. 



Seed Plants 



Juniperns communis monlana Kalmia angustifolia 

 Ledum groenlandicum Kalmia polifolia 



Rhododendron canadcnsc M clampyrum lineare 



The sedge— grass heath association-type. — This occurs in 

 somewhat moister, less exposed situations than the dwarf shrub 

 heath, as for example, or rather dry slopes. The ground is 

 usually covered by a luxuriant growth of cladonias, which may 

 be replaced locally by Racomitrium lanuginosum or occasionally 

 by xerophytic species of Sphagnum, such as 5'. capillaceum 

 tenellum and v?. tenerum. The predominant vascular plants are 

 the sedge, Scirpus caespitosus, and the grass, Calamagrostis 

 Pickeringii. Other herbaceous plants generally present are as 

 follows : 



Lycopodium sitchense Cornus canadensis 



Lycopodium annotinum pungens Prenanthes trifoliolafa 



Deschampsia flexuosa Solidago uliginosa 



Melampyrum lineare Aster nemoralis 



In addition to these, the woody species characteristic of the 

 dwarf shrub-spruce heath are well represented, but for the 

 most part by small specimens, scattered and relatively inconspicu- 

 ous. Like the preceding association-type, the sedge-grass heath 

 is nowhere extensively developed, and it displays a constant 

 tendency to pass over into dwarf shrub-spruce heath. 



The dwarf shruh-spruce heath association-type. — This is one 

 of the most widely distributed and most distinctive types of vege- 

 tation in the barrens. It commonly occupies the upper slopes 



