Beatrice's "sister" is a particularly poisonous plant that her father believes is too potent for him to care for any longer. He tells her that he thinks his "life may pay the penalty" of coming in such close contact with it as caring for it would require and so it "must be consigned to her sole charge" from now on. She calls the "magnificent" plant her "sister" and says that she would be only too happy to take over its care, and she even seems to embrace it with open arms.

Beatrice goes on to attend to the plant with such care that she seems like "one sister performing the duties of affection to another." At one point, she again embraces it, mingling her own breath with its scent, and she asks for its "breath" to revive her from the "common air" that makes her feel faint. She even plucks a flower from it to wear on her dress, and though a drop of its moisture kills a passing lizard, it does no harm to Beatrice at all.

Beatrice has, as she later tells Giovanni, been raised alongside this gorgeous flowering plant so that she feels that it is like her family, and its poison does not harm her as it affects her father, insects, or Giovanni. She says that she "grew up and blossomed with the plant and was nourished with its breath." She has long looked on it as her sister, and she loves it with a "human affection."