  We demonstrate how non-simply-laced gauge and flavor symmetries arise in
F-theory on spaces with non-isolated singularities. The breaking from a
simply-laced symmetry to one that is non-simply-laced is induced by Calabi-Yau
complex structure deformation. In all examples the deformation maintains
non-isolated singularities but is accompanied by a splitting of an I1
seven-brane that opens new loops in the geometry near a non-abelian
seven-brane. The splitting also arises in the moduli space of a probe D3-brane,
which upon traversing the new loop experiences a monodromy that acts on 3-7
string junctions on the singular space. The monodromy reduces the symmetry
algebra, which is the flavor symmetry of the D3-brane and the gauge symmetry of
the seven-brane, to one that is non-simply-laced. A collision of the D3-brane
with the seven-brane gives rise to a 4d N = 1 SCFT with a non-simply-laced
flavor symmetry.
