In a previous paper [EG] we described an integral structure (J,
E) on the exceptional Jordan algebra of Hermitian 3×3
matrices over the Cayley octonions. Here we use modular forms and
Niemeier's classification of even unimodular lattices of rank 24 to
further investigate J and the integral, even lattice
J0=(ZE)⊥ in J. Specifically, we study ring
embeddings of totally real cubic rings A into J which send the
identity of A to E, and we give a new proof of R. Borcherds's
result that J0 is characterized as a Euclidean lattice by its
rank, type, discriminant, and minimal norm.