  We consider a real-valued path; it is possible to associate a tree to this
path, and we explore the relations between the tree, the properties of
$p$-variation of the path, and integration with respect to the path. In
particular, the fractal dimension of the tree is estimated from the variations
of the path, and Young integrals with respect to the path, as well as integrals
from the rough paths theory, are written as integrals on the tree. Examples
include some stochastic paths such as martingales, L\'evy processes and
fractional Brownian motions (for which an estimator of the Hurst parameter is
given).
