かやメ薔薇胚ノ發生ニツイテ

抄録

The embryogeny of Torreya nucifera SIEB. et ZUCC. var. sphacrica KIMURA was studied. In this plant, after fertilization three simultaneous nuclear divisions occur and cell wall formation takes place at the eight nucleate stage. The cells are arranged in two tiers, each consisting of four cells. The cells of the upper tier have no wall toward the centre of the archegonium. The next nuclear division occurs in the upper tier to differentiate the prosuspensor cells, after cutting off the so-called rosette nuclei. After a while, however, these rosette nuclei become disintegrated and the hlbernal embryo of this plant consists of only embryo-initials and completely walled prosuspensor cells.
But in May of the next year, in the rosette region of the proembryo of this plant, development of embryos is commonly seen. So to make clear the origin of these embryos special attention was paid and the following facts were discovered. In the first place the nuclei of some prosuspensor cells move toward the upper extremity of the cells and each of them cuts off a small cell. The cell thus formed can be called also as“rosette cell”. A longitudinal division soon takes place in these rosette cells. By the subsequent divisions of these two cells a rosette embryo is formed. These rosette embryos grow in different directions.
Up to the present, the usual occurrence of the rosette embryo is reported in Pinus and Cedrus. But in these genera the rosette cells are formed definitely in an early stage of the prombryonal development. Thus the formation of the rosette embryo in Torreya in a later stage of development by the subdivisions of the prosuspensor cells appears to be unique among the members of the Coniferales.