Before revision:  Since in growth on flat substrates the linear size of the system remains constant, whereas it increases in the caseof growth on curved substrates, the universality class of{\bf  [  in the long-time limit.
After revision:  Since in growth on flat substrates the linear size of the system remains constant, whereas it increases in the caseof growth on curved substrates, the universality class of{\bf [ ^{1/2 in the long-time limit.