Whenever we rode over in that direction we saw [Lena] out among her cattle, bareheaded and barefooted, scantily dressed in tattered clothing, always knitting as she watched her herd. Before I knew Lena, I thought of her as something wild, that always lived on the prairie, because I had never seen her under a roof. Her yellow hair was burned to a ruddy thatch on her head; but her legs and arms, curiously enough, in spite of constant exposure to the sun, kept a miraculous whiteness which somehow made her seem more undressed than other girls who went scantily lad. The first time I stopped to talk to her, I was astonished at her soft voice and easy, gentle ways. (2.4.38)
It's interesting that Lena and Ántonia both had similar childhoods, but Lena's sexuality and femininity is so much more pronounced than Ántonia's. Jim's reaction to these two girls is, subsequently, different.