The position of Cercidiphyllum among the flowering plants has been the subject of much study and dispute and is still unsettled. The centre of the controversy lies in the inconspicuous apetalous female flower. The view that has long prevailed is that it consists of a calyx and a number of free carpels each with its own style and thus represents, though in a much-reduced and congested form, the same floral structure as is found in Magnolia, Liriodendron, and their allies. In this interpretation, Cercidiphyllum would belong to the Magnoliaceae, or constitute a small related family either on its own or as part, with Trochodendron and perhaps Euptelea, in the Trochodendraceae: but its affinities would lie, whatever its rank, within the Order Magnoliales. A quite contrary view is expressed by Swamy and Bailey (Journ. Arn. Arb., Vol. 30, 1949, pp. 187-210), who hold that what other researchers have regarded as the female flower is really a congested inflorescence, made up of as many individual flowers as there are carpels in the other interpretation, and each subtended by a single bract. If this theory were correct, Cercidiphyllum would have to be regarded as a relic of some primitive type of flowering plant, not related to any other now living. This view has, however, been rejected by Dr Hutchinson (The Genera of Flowering Plants, Vol. 1, 1964), who recognises the distinctness of Cercidiphyllum by placing it in a separate family, the Cercidiphyllaceae, but within the Magnolia alliance, where it is ‘perhaps most nearly related to the genus Liriodendron’.