  We demonstrate the utility of dendrograms at representing the essential
features of the hierarchical structure of the isosurfaces for molecular line
data cubes. The dendrogram of a data cube is an abstraction of the changing
topology of the isosurfaces as a function of contour level. The ability to
track hierarchical structure over a range of scales makes this analysis
philosophically different from local segmentation algorithms like CLUMPFIND.
Points in the dendrogram structure correspond to specific volumes in data cubes
defined by their bounding isosurfaces. We further refine the technique by
measuring the properties associated with each isosurface in the analysis
allowing for a multiscale calculation of molecular gas properties. Using
COMPLETE 13CO(1-0) data from the L1448 region in Perseus and mock observations
of a simulated data cube, we identify regions that have a significant
contribution by self-gravity to their energetics on a range of scales. We find
evidence for self-gravitation on all spatial scales in L1448 though not in all
regions. In the simulated observations, nearly all of the emission is found in
objects that would be self-gravitating if gravity were included in the
simulation. We reconstruct the size-line width relationship within the data
cube using the dendrogram-derived properties and find it follows the standard
relation: s_v ~ R^0.58. Finally, we show that constructing the dendrogram of CO
J=1-0 emission from the Orion-Monoceros region allows for the identification of
giant molecular clouds in a blended molecular line data set using only a
physically motivated definition (self-gravitating clouds with masses 5x10^4
Msun.
