We have developed an improved algorithm that allows us to enumerate the num
ber of site animals on the square lattice LIP to size 46. We also calculate
the number of lattice trees up to size 44 and the radius of gyration of bo
th lattice animals and trees up to size 42. Analysis of the resulting serie
s 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 o
f trees, and confirms to a very high degree of certainty that both the anim
al 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.