著者

熊澤 正夫

出版者

公益社団法人 日本植物学会

雑誌

植物学雑誌 (ISSN:0006808X)

巻号頁・発行日

vol.83, no.982, pp.119-124, 1970

被引用文献数

1

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Seedlings were examined in 13 species of <i>Pittosporum</i> with special reference to the number of the cotyledon and to the vascular supply for the cotyledon. Those species may be divided into three groups (Table 1) in respect of the cotyledonary features. Group I includes the species in which dicotyly seems to be stable; Group II, the species in which seedlings show sometimes syncotyly and monocotyly although normal ones are dicotyledonous; and Group III includes the species in which polycotyly is quite normal, dicotyly being never found.<br>The roots of all the species are usually tetrarch, and in the transition region each metaxylem and phloem are respectively divided laterally into two, the original protoxylem pole of the root being nearly unchanged in its position. Thus eight collateral bundles are formed in the hypocotyl axis (Fig. 1) Each cotyledon is supplied with one pair of these buddies together with one protoxylem pole of the root, as its median strand of the double bundle nature. As a consequence, all primary vascular strands in the hypocotyl are supplied for the cotyledons in the case of the seedlings with four cotyledons. In the seedlings with one or two cotyledons, hypocotylar bundles except those supplied for the cotyledon die out below the cotyledonary node. Seedlings with three or five cotyledons have the root with triarch or pentarch xylem respectively. The pattern of the vascular behaviour in the seedling gives no evidence of the fact that the monocotyly and tetracotyly in <i>Pittosporum</i> have resulted respectively from the fusion and bifurcation of the original two cotyledons.