QUADRATS _ IZI 
a labeled stake at one corner of the quadrat, and locating the latter definitely 
in relation to a conspicuous landmark. When one is in residence for several 
years, practically all chart quadrats are converted into permanent ones, since 
the work already done in the chart quadrat is so much accomplished towards 
the permanent one. This is not necessary when one wishes merely to com- 
pare different areas of stable formations. As a rule, however, some change 
is constantly being wrought by invasion or competition, and the amount and 
direction of this can only be revealed by the permanent quadrat. The latter. 
has a fundamental value for all kinds of invasion, but it is absolutely indis- 
Fig. 53. Permanent quadrat, Polygonile (Polygonum bistortoides) 
Ruxton Park; mapped and photographed July 22, denuded September 
8, 1903. 
pensable in studying complete invasion or succession, and in discovering and 
recording the gradual effects of competition. It is in the detailed investiga- 
tion of these dynamic phenomena that the paramount importance of the 
quadrat is most evident. If the experience of several years be taken as con- 
clusive, no other method is capable of revealing the minute changes as they 
are occurring. 
The permanent quadrat is regularly 1 meter square, a size determined both 
by the exigencies of charting and photographing. When ecograph batteries 
are used, the quadrat is located as close to the latter as is possible. Other- 
