writer may be quoted:--'The rapidity with which it [_i.e._ the group of Flowering Plants] advanced, conquering or supplanting all rivals, may be better understood when we remember that it forms 85% of the flora of the Dakota group '; that is a series of sedimentary rocks in Dakota referred by geologists to the middle of the Cretaceous period(13). In the Wealden rocks of England, which are rich in the remains of Lower Cretaceous plants, no undoubted Flowering Plant has so far been found. [1] For the position of the Cretaceous and other systems in the geological series, see the table on page 42. The more efficient protection of the ovules, the germs which, after fertilisation, become the seeds, the extraordinary variety in the floral mechanisms for assisting cross-pollination, the arrangements for nursing the embryo, and the structural features of the wood in relation both to rapid transport of water and to the storage of food, are factors which have probably contributed to the success of the Angiosperms. The degree of weight to assign to each contributing cause cannot as yet be satisfactorily determined, but the general question raised by the recent origin of these latest products of evolution offers a promising field for work. While admitting our inability at present to do more than suggest possibilities, we may encourage research by speculation. The members of the Vegetable Kingdom placed next to the Flowering Plants are the Gymnosperms or naked-seeded (γυμνὁς, naked) plants, including (i) the Conifers, _e.g._ pines, firs, larches, the yew, etc., (ii) a small group of plants known as the Cycads, whose existing members, now almost confined to a few tropical regions, are the descendants of a vigorous race represented by many species in the floras of the Mesozoic epoch. A third sub-division of the Gymnosperms, the Ginkgoales, is represented by a single survivor, which is described in a later chapter as one of the most remarkable links with the past in the plant kingdom.