She was not doing this consciously, however.

Her motive for inviting them on these expeditions, was simply to include Norman and his friends in her own enjoyment of the summer woods.

It was so easy to turn each excursion into a picnic, to build a fire near some spring and set out a simple lunch that seemed a feast of the gods to voracious boyish appetites.
The goodly smell of corn, roasting in the ashes, or fresh fish sizzling on hot stones gave a charm to the learning of wood-lore that it never could have possessed otherwise.

At first with the heedlessness of city-bred boys, they crashed through the under-brush with unseeing eyes, and unhearing ears, but it was not long until they had learned the alertness of young Indians, following by signs of bark and leaf and fallen feather, trails more interesting than any detective story.
Gradually the old professor, aroused to the fact that they were valuable assistants, began to take some notice of them.

They awakened memories of his own barefooted boyhood, and sometimes when he had had a particularly successful morning, he threw off his habitual abstraction, and as Mary reported to Jack, was "as human as anybody." It seemed, too, that at these times he saw Mary in a new light; saw her as the boys did, fearless as one of themselves, tireless as a squaw, and a happy-go-lucky comrade who could turn the most ordinary occasion into a jolly outing.