Criteria are given under which the boundary of an oriented surface does not
consist entirely of trajectories of the C-1 differential equation (x) over
dot = f(x) in R-n. The special case of an annulus is further considered, a
nd the criteria are used to deduce sufficient conditions for the differenti
al equation to have at most one cycle. A bound on the number of cycles on s
urfaces of higher connectivity is given by similar conditions.