How does Marie de France use imagery in The Lais of Marie de France?

Marie uses allegorical language and images throughout the lais. The character Le Fresne, for instance, which can be translated as "ash tree", is so named because she was left and later discovered in an ash tree. Meanwhile, her twin sister is named La Codre, which can be translated as "hazelnut tree". She uses another plant analogy in the lay entitled Chevrefoil, which is French for honeysuckle. At the end of this short lay, she compares the love of Tristram and Isolde to honeysuckle growing on a hazelnut tree. Each supports the other, and if one dies so does the other. In the narrative, Tristram leaves his sign for Isolde carved on a stick of hazel wood.