Let X be a smooth projective curve of genus g ≥ 2 defined over an arbitrary algebraically closed field K. For any vector bundle E on X, call μ(E) := deg(E)/rank(E) the slope of E. A vector bundle E on X is said to be spanned if the natural map H(X,E)⊗OX → E is surjective. Such bundles are important tools for the projective geometry ofX because they are exactly the vector bundles associated to a...