1922] McDOUGALL—SYMBIOSIS 203 
amount of soil water. A number of measurements of soil tempera- 
. ture were made in both the higher and lower parts of the forest at 
depths of three inches and twelve inches, but temperatures taken 
in different parts of the forest on the same day and at the same 
depth were found to be almost exactly the same. Tests were made 
also for soil acidity in different parts of the forest, using the indicator 
method described by WHERRY.* The results of these tests showed 
that the soil of the forest is neutral throughout. Although no 
chemical analyses have been made, there is no reason for thinking 
that the mineral constituents of the soil are not practically the 
same throughout the forest. 
THE PLANT COMMUNITY 
MeEtTHOps.—Before the more special types of symbiosis can be 
studied adequately in any plant community, it is necessary to have 
a thorough understanding of the structure of the community and 
of the disjunctive social symbiosis, that is, of the gross inter- 
relations of the component parts of the vegetation. In order to 
obtain this information, the entire forest was first staked out into 
one hundred foot quadrats. The only reason for choosing the one 
hundred foot quadrat instead of a unit of the metric system was 
that one hundred foot steel surveyor’s tapes are readily obtained 
and are convenient to use. No attempt was made to have the 
quadrats exactly one hundred feet square. The tapes were fastened 
to the stakes by means of straps, and these were of such a length 
-that on level land and with the tapes drawn tight the stakes would 
be about one hundred two feet apart. In the woods, however, 
with the tapes running among shrubs, between trees, over fallen 
logs, etc., and with the tape never very tightly drawn, the quadrats 
were approximately one hundred feet square. It was found that 
by making fractional quadrats across each end of the woods and 
part way along one side, to where there is a jog in the boundary 
line, there were then 216 full size quadrats (fig. 1). 
Having subdivided the forest into quadrats, two methods were 
used for locating and mapping the components of the vegetation. 
The first method was used only for the trees and shrubs. Two 
4 Wuerry, E. T., Soil acidity and a field method for its measurement. Ecology 
1: 160-173. 1920 
