Diagram illustrating crossdating and the extension of a dated ring width chronology backward in time. 6. Crossdating: It is most important principle of dendrochronology. The yearly ring widths must be crossdated among all radii within a stem andamong different trees in a given stand, as well as among ring-width patterens of neighboring stands. The crossdating can be obtained itself is evidance that there is some climatic or environmental information common to the sample trees. Sometimes during ayear of extreme climate a tree may not form a ring on all portionss of the stem. The ring is then said to be partial, locally absent or missing along certainstem segments or radii. At