  The typical island distance $\ell$ in submonlayer epitaxial growth depends on
the growth conditions via an exponent $\gamma$. This exponent is known to
depend on the substrate dimensionality, the dimension of the islands, and the
size $i^*$ of the critical nucleus for island formation. In this paper we study
the dependence of $\gamma$ on $i^*$ in one--dimensional epitaxial growth. We
derive that $\gamma = i^*/(2i^* + 3)$ for $i^*\geq 2$ and confirm this result
by computer simulations.
