From the summary: An ordered graph is a graph together with a linear order on its vertices. A hereditary property of ordered graphs is a collection of ordered graphs closed under taking order-preserving isomorphisms of the vertex set, and order-preserving induced subgraphs. If ${\cal P}$ is a hereditary property of ordered graphs, then ${\cal P}_n$ denotes the collection $\{G\in{\cal P}: V(G)=[n]\}$, and the function $n\mapsto\vert{\cal P}_n|$ is called the speed of ${\cal P}$. In this paper we determine the possible speeds of a hereditary property of ordered graphs, up to the speed $2^{n-1}$. In particular, we prove that there exists a jump from polynomial speed to speed $F_n$, the Fibonacci numbers, and that there exists an infinite sequence of subsequent jumps, from $p(n)F_{n,k}$ to $F_{n,k+1}$ (where $p(n)$ is a polynomial and $F_{n,k}$ are the generalized Fibonacci numbers) converging to $2^{n-1}$. Our results generalize a theorem of {\it T. Kaiser} and {\it M. Klazar} [Electron. J. Comb. 9, Research paepr R10 (2002‒2003; Zbl 1015.05002); printed version J. Comb. 9, No. 2, R10 (2002‒2003)] who proved that the same jumps occur for hereditary properties of permutations.