  Let M be a spin manifold with a circular action. Given an elliptic curve E,
we introduce, as in Grojnowski, elliptic bouquets of germs of holomorphic
equivariant cohomology classes on M. Following Bott-Taubes and Rosu, we show
that integration of an elliptic bouquet is well defined. In particular, this
imply Witten's rigidity theorem.
  We emphasize the similarity between integration in K-theory and in elliptic
cohomology.
