  The shape assumed by a slender elastic structure is a function both of the
geometry of the space in which it exists and the forces it experiences. We
explore by experiments and theoretical analysis, the morphological phase-space
of a filament confined to the surface of a spherical bubble. The morphology is
controlled by varying bending stiffness and weight of the filament, and its
length relative to the bubble radius. When the dominant considerations are
geometry of confinement and elastic energy, the filament lies along a geodesic
and when gravitational energy becomes significant, a bifurcation occurs, with a
part of the filament occupying a longitude and the rest along a curve
approximated by a latitude. Far beyond the transition, when the filament is
much longer than the diameter, it coils around the selected latitudinal region.
A simple model with filament shape as a composite of two arcs captures the
transition well and for better quantitative agreement with the subcritical
nature of bifurcation, we study the morphology by numerical energy
minimization. Our analysis of filament's morphological space spanned by a
geometric parameter, and one that compares elastic energy with body forces, may
provide guidance for packing slender structures on complex surfaces.
