162 THE FORMATION 
not necessary in reconnaissance, nor do they displace general methods of 
real value. The use of the latter in even a supplementary way will grad- 
ually be discontinued, however, as fields become smaller by reason of in- 
crease in the number of workers, and as the need for precise methods 
becomes more universally felt. 
The quadrat constitutes the initial concept from which all the methods 
have grown. In itself, it has givén rise to a variety of quadrats applicable 
to the most fundamental problems of vegetation. From it have come, on 
the one hand, the migration circle, and on the other, the transect. The 
latter in turn has yielded the ecotone chart, and the layer chart. All of 
these are based upon direct and detailed contact with vegetation itself, and 
permit accurate recording of all the results obtained. ; 
QUADRATS 
199. Uses. In its simplest form, the quadrat, as the name implies, is 
merely a square area of varying size marked off in a formation for the pur- 
pose of obtaining accurate information as to the number and grouping of the 
plants present. As indicated above, it was first used for determining the 
abundance of the various species of a formation. This made it possible to 
ascertain the relative rank of the species of layers and formations, and 
enabled one for the first time to gain some idea of the minute structure of 
a bit.of vegetation. The results were at once applied to the task of establish- 
ing a numerical basis for abundance, and of working out a new system of 
abundance to correspond. The quadrat method was also used to determine 
the character of seasonal aspects, and to yield a knowledge of the exact 
differences in diverse areas of the same formation. Incidentally, the deter- 
minations of abundance were made the basis of an actual census of certain 
alpine formations. This, while it was extremely interesting to find that a 
square mile of alpine meadow contained approximately 1,500,000,000 plarts, 
was confessedly destitute of ecological value. The most important applica- 
tions of the quadrat idea were made by Clements? in the chart, the perma- 
nent and the denuded quadrats. The development of these was due to the 
fact that zones or formations permit of comparison upon floristic as well 
as physical grounds, and that a detailed record of their structure is necessary 
for this purpose. Similar comparisons are necessary for the consocies, 
zones, and patches of the same formation, and the quadrat becomes an in- 
dispensable means for studying alternation and zonation. For the investi- 
1The Development and Structure of Vegetation, 84. 1904. 
THORNBER, J.J. The Prairiegrass Formation in RegionI. Rep. Bot. Surv. Neb., 
5:29. 1901. 
