We show that the set of positive solutions of semilinear Dirichlet pro
blem on a ball of radius R in R-n Delta u + lambda f(u) = 0 for \x\<R,
u = 0 on \x\ = R consists of smooth curves. Our results can be applie
d to compute the direction of bifurcation. We also give an easy proof
of a uniqueness theorem due to Smeller and Wasserman (1984).