ParticleSystem dynamic batching doesn't work

I use ParticleSystem and render mode is Mesh, but the dynamic batching doesn’t work, objects use the same mesh and material. If i chooses render mode to other way, like billboard, it works.
Why? anyone knows it?

Thanks.

The section from Draw Call Batching manual page specifies the criteria for dynamic batching as:

Batching dynamic objects has certain
overhead per vertex, so batching is
applied only to meshes containing less
than 900 vertex attributes in total.

  • If your shader is using Vertex Position, Normal and single UV, then
    you can batch up to 300 verts; whereas
    if your shader is using Vertex
    Position, Normal, UV0, UV1 and
    Tangent, then only 180 verts.

Which is an important part since when your render mode is billboard the number of vertices must be satisfying the vertices count for this but when you choose a mesh the vertices count is exceeding these limits and hence you are not being benefited with dynamic batching. You can just check this by looking at the Vertices count from Stat when you switch between billboard and mesh render mode.