  We have developed an improved algorithm that allows us to enumerate the
number of site animals on the square lattice up to size 46. We also calculate
the number of lattice trees up to size 44 and the radius of gyration of both
lattice animals and trees up to size 42. Analysis of the resulting series
yields an improved estimate, $\lambda = 4.062570(8)$, for the growth constant
of lattice animals, and, $\lambda_0 = 3.795254(8)$, for the growth constant of
trees, and confirms to a very high degree of certainty that both the animal and
tree generating functions have a logarithmic divergence. Analysis of the radius
of gyration series yields the estimate, $\nu = 0.64115(5)$, for the size
exponent.
