In a few words, these are the main characters of the large group of _Cordaites_, which held the dominant position among Gymnosperms in the Palæozoic era. They have relationships, or perhaps one should say likenesses, to many groups. Their stem- and root-anatomy is similar to the Coniferæ of the present day, the position of the ovules is like that in the Taxaceæ, the male cones in some measure recall those of _Ginkgo_, the anatomy of their leaves has points which are comparable with those of the Cycads, to which group also the large pith in the stem and the structure of some details in the seeds unite them. Their own specially distinctive characters lie in their crown of huge leaves, and unbranched shaft of stem, the similarity of their male and female inflorescences, and some points in their pollen grains which have not been mentioned. The type is a very complex one, possibly coming near the stock which, having branched out in various directions, gave rise to several of the living families. [Illustration: Fig. 64.—Representation of _Cordaites_ Seed and its Axis with Scales, slightly diagrammatic, modified from Renault. A, Axis with _s_, scales; _c_, coat of the seed, from which the inner parts have shrunk away; _n_, nucellus; _p.c_, pollen chamber containing pollen grains which enter through _m_.] Plants which come very near to the Cordaiteæ are the Poroxyleæ. Of this group we have unfortunately no remains of fructifications in organic connection, so that its actual position must remain a little doubtful till they are discovered. There seems no doubt that they must have borne seeds. Still, it has been abundantly demonstrated in recent years that the anatomy of the root, stem, and leaves indicates with considerable exactness the position of any plant, so that, as these are known, we can deduce from them, with a feeling of safety, the position that _Poroxylon_ takes in the natural system. In its anatomy the characters are those of the Cordaiteæ, with certain details which show a more primitive nature and seem to be characteristic of the groups below it in organization.