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1903] FLORA OF NORTH CAROLINA 257 
development and the life-activity of these organisms and their 
decomposition after death. The character of the plant growth, 
for example, plays not only a direct, but an intermediate réle in 
the formation of soil. The relief of the soil has an important 
influence in determining the drainage, temperature, etc. And 
lastly, the successive changes which have taken place in the 
climate, the encroachments of the forests, the spread of marshes, 
the drying up of the soil, etc., must in their turn influence the 
character of soils. A knowledge of the laws and the forms of 
these influences makes it possible to obtain from the study of 
soils a basis for the reconstitution of the recent past of the 
country and for sketching its recent geophysic and geobiologic 
history. An inspection of the soils of western North Carolina 
reveals a close relationship between the vegetal covering and the 
soil. There are a number of humus dwellers with ectotrophic 
and endotrophic mycorhiza. Such plants as the oaks, beeches, 
chestnuts, poplars, willows, pines, spruces, and firs are provided 
with ectotrophic mycorhiza and therefore are to a certain extent 
dependent on the humus of the soil. Without it a dense forest 
could not exist, and in any region, such as the mountainous area 
of North Carolina, the luxuriance of the forest is a correlative of 
the richness of the soil in humus and its mechanical condition, 
and vice versa.** Plants with endotrophic mycorhiza also add 
their quota to the upbuilding and maintenance of the forest 
litter, and so do many fungi. In North Carolina, as elsewhere, 
the rotten windfalls and the fallen leaves return many valuable 
ingredients to the earth. In the North Carolina mountains, if 
undisturbed by man, a deep soil rich in organic detritus is found, 
and this clearly points to the long occupation of the territory by 
dense forests. 
These introductory remarks have been made to show the 
delicate balance which exists between the vegetation of western 
North Carolina, on the one hand, and the soil and physiographic 
features, on the other. Constant change has been manifested in 
* Another indication of a soil rich in humus is a great variety of saprophytic 
fungi belonging to several well-recognized groups, such as the Polyporei, Agari- 
cineae, etc. 
