1922] McDOUGALL—SYMBIOSIS 205 
rows of quadrats were surveyed at the same time. A hundred 
foot tape was stretched between the first two quadrats of the first 
two rows. Then while walking through these quadrats in the 
directions indicated in fig. 2, counts were made of all species of trees 
and shrubs present. The frequency of the occurrence of each 
species of shrub was indicated by the numerals 1, 2, 3, and 4; 
no. 1 indicating only one to three specimens in the quadrat, no. 4 
indicating great abundance, and nos. 2 and 3 representing inter- 
mediate degrees of frequency. In the case of trees the actual 
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Fic. 2.—Two one-hundred-foot quadrats illustrating method used in making 
counts of trees and shrubs in University woods: heavy line between quadrats indi- 
cates position of steel tape; arrows show direction taken by surveyor in making 
counts. 
number of individuals of each species was noted. After counts in 
these two quadrats had been completed, the tape was taken up 
and stretched between the next two quadrats and counts made 
there in a similar way, the procedure being repeated until the 
entire forest had been surveyed. Having secured these data, a 
distribution map was made for each species (fig. 1). No attempt 
was made to locate the individuals within the quadrat, but only to 
place them in the quadrats in which they occur. Each individual 
is shown on the maps, therefore, within one hundred feet or less of 
its actual position in the forest. 
For the herbaceous vegetation a somewhat different method was 
used. Only one row of quadrats was surveyed at a time and no 
