We construct an element in a direct product of finite dimensional modules over a string algebra such that the pure-injective envelope of this element is a superdecomposable module.A nonzero module M is said to be superdecomposable if M has no indecomposable direct summands. For example, let R be the endomorphism ring of a countable dimensional vector space V , and let I be the ideal of R consisting of all endomorphisms with finite dimensional images. If R = R/I and e is a projection on a subspace of V whose image and coimage are infinite dimensional, then R ∼ = e R ⊕ (1 − e)R as a right module over itself and R ∼ = e R ∼ = (1 − e )R . Furthermore, every nontrivial decomposition of R as a right module is of this form; therefore R is superdecomposable.For more examples, let R = k X, Y be a free algebra over a field k, and let E = E(R R ) be the injective envelope of R considered as a right module over itself. It is easily verified (see [11, Prop. 8.36]) that R R has no nonzero uniform submodules. Therefore the same is true for E, and hence E is a superdecomposable injective module.More generally, this is a common feature of finite dimensional wild algebras, that they usually (conjecturally always) have a superdecomposable pure-injective module (see [11, Ch. 8] for a list of existing results). Here a module M over a finite dimensional algebra A is pure-injective if M is a direct summand of a direct product of finite dimensional A-modules.If A is a tame finite dimensional algebra over a field, it has been believed for a while (see [24, p. 38]) that every pure-injective A-module has an indecomposable direct summand. But recently, Puninski [19] showed that every nondomestic string algebra over a countable field has a superdecomposable pure-injective module (note that every string algebra is tame). The main drawback of his proof is that it depends on the cardinality of the ground field and is highly nonconstructive. Specifically, it is based on a quite ingenious construction of Ziegler [26] which seems to work only for countable fields.