根の原初木部の数からみた <i>Metasequoia</i> の類縁関係

Abstract

In the present paper reports are made on the structure of roots in Metasequoia and its affinity to other conifers as represented by the structure of roots. The results can be summarized of follows.1) The structure of roots in Metasequoia is not much different from that of the other conifers.2) According to the number of protoxylem Taxodiaceae can be divided into the following three groups: 1st Group……Diarch both in the long and the short root. Sciadopitys verticillata Sieb. et Zucc., Taiwania cryptomerioides Hayata, Cunninghamia lanceolata Hook. 2nd Group……Tri-, tetra- or polyarch in the long root and di- or triarch in the short root. Sequoiadendron gigantium Buch., Glyptostrobus pensilis Koch., Taxodium distichum Rich., Metasequoia glyptostroboides Hu et Cheng, Sequoia sempervirens End1. 3rd Group……Triarch both in the long and the short root. Cryptomeria japonica Don.3) Differing from the second group to which belongs Metasequoia, the representatives of the first group have many remarkable characters in common. Their pollen tube branches and the proembryo has rosette-cells.4) Among the representatives of the second group no remarkable difference in morphological characters are seen. It seems not adequate to separate Metasequoia from the other members as a representative of a special family, Metasequoiaceae.