双花木属和壳菜果属(金缕梅科)的核型研究

本文对金缕梅科Hamamelidaceae双花木属Disanthus Maxim．的长柄双花木D．cercidifolius subsp．longipes和单种属壳菜果属Mytilaria Lec.首次进行了染色体计数和核型分析。结果表明：长柄双花木与产自日本的双花木D. cercidifolius subsp．cercidifolius的体细胞染色体数目一致，均为2n＝16，前者无“st”或“t”染色体，表明该亚种可能比较原始；壳菜果Mytilaria laosensis Lec．的染色体数目为2n＝26，x=13。前人报道的金缕梅科染色体基数为x＝8和x＝12，因此x＝13可能是金缕梅科的一个新染色体基数。联系该属的形态特征及其与马蹄荷属Exbucklandia R．W．Brown的关系，作者支持将壳菜果属处理为独立的亚科，即壳菜果亚科Mytilarioideae。

KARYOTYPES OF DISANTHUS AND MYTILARIA (HAMAMELIDACEAE)

Reported in the present paper are chromosome numbers and karyotypes of two monospecific genera, Disanthus Maxim, and Mytilaria Lee. in the Hamamelidaceae. Disan-thus cercidifoltus subsp. longipes (H. T. Chang) K. Y. Pan, distributed in China, was found to have the same chromosome number as the subsp. cercidifolius in Japan, i. e. 2n = 16, with x = 8. The interphase nuclei were of the simple-complex chromocenter type, and the mitotic prophase chromosomes were of the proximal type. Remarkable differences in karyotype were found between the two subspecies; the former with 2n = 2x = 16=6m 10 sm, while the latter with 2n = 2x=16 = 6m 6sm 4st (t). The absence of st ( or t) chromosomes in subsp. longipes, together with gross-morphological evidence, suggest that this subspecies be more primitive than the other. Mytilaria laosensis Lee. was found to have interphase nuclei of the simple-complex type, and mitotic prophase chromosomes of the proximal type. The chromosome number was 2n = 26 with x=13 and the karyotype was 2n = 2x= 26= 22m 4sm (1SAT). This is the first chromosome report for this genus. The basic chromosome number, x = 13, might be a new one for the whole Hamamelidaceae. The present authors support the treatment of Mytilaria as an independent subfamily, Myti-larioideae, considering its morphological characters and relationships with the genus Exbuck-landia.