  We discuss the problem of the vanishing of Poincar\'e series. This problem is
known to be related to the existence of weakly holomorphic forms with
prescribed principal part. The obstruction to the existence is related to the
pseudomodularity of Ramanujan's mock theta functions. We embed the space of
weakly holomorphic modular forms into the larger space of harmonic weak Maass
forms. From this perspective we discuss the linear relations between Poincar\'e
series and the connection to Ramanujan's mock theta functions.
