Were they ad libbing?

Or were the actors and the scriptwriters just that good? I'm thinking of a couple of scenes -- first, when Mama, Papa and Nels are worrying over the disposal of Uncle Elizabeth, and both Kristin and Katrin trip as they walk behind Mama to take Dagmar's lunch to her, upstairs. Mama says almost as an ad lib, "And pick up your feet."

In the early, Saturday-night budget sequence, when Mama gives Kristin a dime for a new notebook, she tells her to be careful not to lose the money, which she's put in her hanky, and again almost it seems an ad lib when she says, "Don't blow your nose."

I know on one hand it seems pretty unusual that scriptwriters and directors would let this sort of thing go on, especially on a movie with a budget that was so large, but if anybody could pull off the adlibs, I think it would have been actors of the stature appearing in this film, especially Miss Dunne.