"The art on the western face of this early structure is unlike anything in the Maya realm. Painted white and embellished with rows of four-petal flowers and small stylized insects, birds, and animals, this wall must have been commissioned to a codex (bark paper book) artist. It is not a mural, but more a wall painting.
Even at this early date, realism of flowers was adhered to, just as realism in portraiture was to follow shortly. Although the Maya did not know that the stamen were "male" and the stigma were "female" elements of the flower, they did attribute duality to all living things. The paired extensions of the four petal flowers on this wall are all shown, and these artists would have known that these go into the heart of the flower." [This article has a reconstruction drawing of the western wall of House E and its floral motifs, plus botanical cross-sections of flower parts which Robertson maps into the mural flowers.]
Merle Green Robertson, "Sculpture and Murals of the Usumacinta Region," in MAYA (Palazzo Grassi, Venice), p. 297-99