金缕梅科的种子形态学及其系统学评价

本文利用光学显微镜及扫描电镜在属级水平上观察了金缕梅科全部6亚科中的21属41种1变种植物的种子特征，结果表明：该科的种子形状、颜色、大小及种脐特征在各亚科中有差异(除了双花木亚科与金缕梅亚科的大多数属是一致的)可作为区分亚科的特征之一。根据种皮的特征，可划分为5类：(1)种皮平滑或仅在边缘部分具条纹状纹饰(双花木亚科及金缕梅亚科中大部分属)；(2)种皮具条纹状纹饰，条纹有波浪加厚或升高(马蹄荷亚科)；(3)种皮具瘤状纹饰或具条纹和瘤状相间排列的纹饰(红花荷亚科)；(4)种皮具条一网状纹饰(壳菜果亚科)；(5)种皮具网状纹饰(枫香亚科)。种皮纹饰对亚科的划分具有一定意义。此外，还详细观察了该科的种皮结构，确认金缕梅科的种皮由外种皮及内种皮构成，而外种皮又进一步划分为外层、中层和内层，种皮各层的细胞层数对该科的分类价值不大。研究结果还表明：枫香亚科的种子特征明显不同于该科的其它成员。关于枫香亚科的系统位置还需深入研究。

THE SEED MORPHOLOGY IN HAMAMELIDACEAE AND ITS SYSTEMATIC EVALUATION

The seed coat of 41 species and one variety, representing six subfamilies in the family Hamamelidaceae, was examined using light microscope ( LM) and scanning electron microscope (SEM). The results indicate that there are some differences between the subfamilies in characters such as seed shape, color, size and hilum, but the subfamily Disan-thoideae and most genera in the subfamily Hamamelidoideae have similar seed morphology. The above-mentioned characters are, therefore, of certain value for classification between subfamilies. The seed coat morphology under SEM could be mainly divided into five types: (1) Smooth or only striate at the margin of seeds, e. g. , Disanthoideae and most genera in Hamamelidoideae (in Ostrearia, Parrotia and Matudaea, seed coat was almost smooth, but with irregular tuber-projection); ( 2 ) Striate, with striae undulate-thickened or raised, e. g. , Exbucklandioideae; ( 3 ) Tuberculate or striate-tuberculate, e.g., Rhodoleioideae; (4) Striate-reticular, e.g. , Mytilarioideae; (5) Reticular, e.g. , Liquidambaroideae. The seed coat sculpture could be served as an important criterion of distinguishing subfamilies. The testa structure of this family was also minutely studied in the present paper. The study shows that seed coat is composed of identical testa (it consisting of exotesta, mesotesta and endotesta) and tegmen, and is confirmed to be a constant sturcture in the Hamamelidaceae. In addition, some differences were reported in number of cell layers of the testa in the different genera, but according to our study, these differences seemed to be not significant for the delimitation of genera or subfamilies in this family. Notably, the subfamily Liquidambaroideae differs distinctly from the other subfamilies in seed morphology. The sys- tematic position of the Liquidambaroideae needs to be further studied.