A problem which has long been discussed, and which has aroused much interest, is the relative antiquity of the Monocotyledonous and the Dicotyledonous branches of the flowering plants. A peculiar fascination seems to hang over this still unsolved riddle, and a battle of flowers may be said to rage between the lily and the rose for priority. Recent work has thrown no decisive light on the question, but it has undoubtedly demolished the old view which supposed that the Monocotyledons (the lily group) appeared at a far earlier date upon this earth than the Dicotyledons. The old writers based their contention on incorrectly determined fossils. For instance, seeds from the Palæozoic rocks were described as Monocotyledons because of the three or six ribs which were so characteristic of their shell; we know now that these seeds (_Trigonocarpus_) belong to a family already mentioned in another connection (p. 72), the Medulloseæ (see p. 122), the affinity of which lies between the cycads and the ferns. Leaves of _Cordaites_, again, which are broad and long with well-marked parallel veins, were described as those of a Monocotyledonous plant like the Yucca of to-day; but we now know them to belong to a family of true Gymnosperms possibly distantly related to _Taxus_ (the Yew tree). Recent work, which has carefully sifted the fossil evidence, can only say that no true Monocotyledons have yet been found below the Lower Cretaceous rocks, and that at that period we see also the sudden inrush of Dicotyledons. Hence, so far as palæontology can show, the two parallel groups of the flowering plants arose about the same time. It is of interest to note, however, that the only petrifaction of a flower known from any part of the world is an ovary which seems to be that of one of the Liliaceæ. In the same nodules, however, there are several specimens of Dicotyledonous woods, so that it does not throw any light on the question of priority. With the evidence derived from the comparative study of the anatomy of recent flowering plants we cannot concern ourselves here, beyond noting that the results weigh in favour of the Dicotyledons as being the more primitive, though not necessarily developed much earlier in point of time. Until very much more is discovered than is yet known of the origin of the flowering plants as a whole, it is impossible to come to a more definite conclusion about this much-discussed subject. Let us now attempt to picture the vegetable communities since the appearance of the flowering plants. The facts which form the bases of the following conceptions have been gathered from many lands by numerous workers in the field of fossil botany, from scattered plant remains such as have been described.