THE GINKGO. The fourth great group of living gymnosperms contains at present but a single form, the Ginkgo, a remarkable tree almost un known in the wild state, but recently reported in certain forests of Western China. Its extensive cultivation, however, in connection with temple worship in China and Japan has preserved it, and has introduced it as a well-known park tree in all civilized countries. The leaves so much resemble those of the maidenhair fern that they suggest the common name 'maidenhair tree.' The fruit is plum-like. See GINKGO.
It is thought that gymnosperms have been de rived from the ferns, from which they differ most strikingly in their production of seeds. Among the numerous other characters which separate the gymnosperms from the angiosperms, it may be mentioned that the female generation (garnet°. phyte) developed within the ovule (see ALTER NATION OF GENERATIONS) bears such female or gans as are found in the ferns and the mosses (archegonia) ; in angiosperms no such organs are found. Again, in gymnosperms the body of the stem is chiefly composed of the peculiar form of vessels called tracheid (q.v.), which differ from the true vessels of angiosperms in not form ing somewhat continuous passageways. These tracheids are formed so regularly that the wood is remarkably uniform and of even grain, a fea ture characteristic of the lumber obtained from pines and their allies. The fruits of gymno
sperms are diverse, and from the fact that the seeds are not inclosed they are different in char acter from those of angiosperms. The best-known form of fruit is the prominent cone that gives name to the group Coniferw. These cones en large very much during the formation of the seeds, and consist of an axis bearing numerous bract-like members to the upper surface of which the seeds are attached. In the case of the cy cads and ginkgo, the seed itself ripens and re sembles a fleshy stone fruit, such as a plum or cherry. To botanists gymnosperms are of chief interest because of their relations to the ferns and to the angiosperms. The largest problems in connection v'ith the group have to do with the details of their origin from the ferns, and with the more obscure question as to whether they in turn may have given rise to the angiosperms.
In addition to the books cited under MORPHOL OGY. all of which treat more or less fully of this group, consult Coulter and Chamberlain, Mor phology of Spermatophytes, part i. (New York, 1901). For works on classification, see under TAXONOMY. See DISTRIBUTION OF PLANTS.