Provides a data.frame with 18838 rows and 7 columns containing data on:
[ ,1] ID = Site and species id <factor>
[ ,2] CID = Unique cell id <integer>
[ ,3] YEAR = Year of the ring <integer>
[ ,4] CA = Lumen size (micron) <numeric>
[ ,5] XCAL = X-value of cell center in calibrated coordinate system (micron) <numeric>
[ ,6] YCAL = Y-value of cell center in calibrated coordinate system (micron) <numeric>
[ ,7] CWTALL = Mean thickness of all cell walls (micron) <numeric>