  This paper addresses the problem of wellposedness of non-autonomous linear
evolution equations $\dot x = A(t)x$ in uniformly convex Banach spaces. We
assume that $A(t):D \subset X\to X$, for each $t$ is the generator of a
quasi-contractive $C_0$-group where the domain $D$ and the growth exponent are
independent of $t$. Well-posedness holds provided that $t\mapsto A(t)y$ is
Lipschitz for all $y\in D$. H\"older continuity of degree $\alpha<1$ is not
sufficient and the assumption of uniform convexity cannot be dropped.
