幼苗期に於ける荳科地下子葉類の外部形態から観た維管束の分れ方について

抄録

Anatomical studies were carried out upon the vascular differentiation in leguminous plants. Thirteen species were used as material in the present study. They were sown in seed-boxes filled with sandy loam at the seasons favorable for the growth of individual species. Serial free-hand sections were stained with 0.5∼1 per cent fuchsin solution. The results were as follows : (with a text figure) (1) With regard to the root xylem, eight of the species investigated were of triarch and the other five were of tetrarch. In general, the transition region between root and stem was commonly very short, but in all the triarchy plants and Vicia Faba, this region were found to extend to the first or to the third, or even to the fourth nodes above the cotyledons. And it was of interest that all the triarchy plants were found belonging to the hypogaeous group. On the other hand, the vascular transition in the tetrarchy species, excluding V. Faba, occured in the hypocotyl. (2) In those nine species, namely, eight triarchy and V. Faba there occured no transition in the hypocotyl, but a new vascular bundle were formed by the breaking of the original two xylem strands which had departed from the cylinder as cotyledonary traces. The root xylems in V. Faba proved to be six in number, and two xylems of them were formed by the breaking of the strands of special courses. In tetrarchy plants, the bundles distributing in the region just beneath the cotyledonary node were six and ten in number, but according to the first forking of vascular bundles, these plants are usually classified into two grades, e. g. six and eight. (3) The traces supplying a single cotyledon ranged in number from one to two, and they were associated with breakings or fusions in the stele around and above the point of departure of the trace : One trace among those traces, however, was formed only by the differentiation of triarchy plants, but the other plants pocessed two traces. Thus the number of the cotyledonary traces in the hypogaeous plants were found usually less than that in the epigaeous. (4) With regards to first internodal region, nine hypogaeous species were found different in the differentiation and arrangement of vascular tissues from the epigaeous plants. At the part just above the cotyledonary node, two cortical bundles separated from the cotyledonary trace, and developed into the lateral leaf trace or into the stipular trace, through one or more internodes. And within a short time, two fiber strands projected from the distal parts of the stele. The strand supplying the median trace of petiole and the axillary bud was derived from this strand at each sides. The vascular bundles in the stele ranged from two to eight in number. (5) In the nine species, there were observed two developmental phases of leaf on stem. V.hirsuta, V.tetrasperma, V.Faba and P.sativum were found to have a foliage leaf on the third node, while the other five species had it on the fourth node. on the other hand, the foliage leaf of tetrachy plants was observed even on the first node, similar to most epigaeous plants. (6) The differentiation of xylems and fiber strands in the cortical layer associated with the number of leaf trace. In general, the cortical strands run out from the main axis, between the second and the fourth node to foliage tissues. And it was found that the disappearance of these vascular component from the cortical layer were closely related to the transition of bundles in the stele. (7) The mode of differentiation of vascular bundles at the second or following internode and nodal region in the four tetrarahy plants was very similar to that after the vascular transition in the triachy species. (8) From the facts above mentioned, it is clear that, there are various types of differentiation, but the differentiation is concerned with the morphological characters of the species, and also some hypogaeous leguminous plants have a systematical differentiation of vascular bundles.