Coniferales (see p. 90). _Araucareæ_, _e.g._ Monkey-puzzle Genera both living and fossil. Fossil forms undoubted so far back as the Jurassic, and presumably further. _Abietineæ_, _e.g._ Pine and Larch Genera both living and fossil. Fossils recognized as far back as the Lower Cretaceous. _Cupresseæ_, _e.g._ Juniper, Cypress Genera both living and fossil. Fossils recognized as far back as the Jurassic. _Taxeæ_, _e.g._ Yew Genera living and fossil. Fossils recognized as far back as the Cretaceous. Cordaitales (see p. 92). _Cordaiteæ_, _e.g._ Cordaites Fossil only. Characteristic of Devonian, Carboniferous, and Permian periods. _Poroxyleæ_, _e.g._ Poroxylon Fossil only. Characteristic of the Carboniferous and Permian. Ginkgoales (see p. 98). _Ginkgoaceæ_, _e.g._ Ginkgo Fossil and living, dating back, apparently with little change, to Palæozoic times. We must pay the most attention to the two last groups, as they are so important as fossils, and the _Cordaiteæ_ were a very numerous family in Coal Measure times. They had their period of principal development so long ago that it is probable that no direct descendants remain to the present time, though some botanists consider that the _Taxeæ_ are allied to them. Of the groups still living it is difficult, almost impossible, to say which is the highest, the most evolved type. In the consideration of the Gymnosperm family it is brought home with great emphasis how incomplete and partial our knowledge is as yet. Many hold that the _Araucareæ_ are the most primitive of the higher Gymnosperms. In support of this view the following facts are noted. They have a simple type of fructification, with a single seed on a simple scale, and many scales arranged round an axis to form a cone. In the microscopic structure of their wood they have double rows of bordered pits, a kind of wood cell which comes closer to the old fossil types than does the wood of any of the other living genera. Further than this, wood which is almost indistinguishable from the wood of recent Araucarias is found very far back in the rocks, while their leaves are broad and simple, and attached directly to the stem in a way similar to the leaves of the fossil _Cordaiteæ_, and very different from the needle leaves on the secondary stems of the Pine family; so that there appears good ground for considering the group an ancient and probably a primitive one.[10]