七筋姑属叶表皮形态特征及其系统学意义

THE LEAF EPIDERMAL FEATURES AND THEIR SYSTEMATIC SIGNIFICANCE OF THE GENUS CLINTONIA RAF

利用扫描电镜和光镜对七筋姑属北美全部4种和东亚1种11个居群的叶表皮形态进行了观察。其总体特征如下：上表皮细胞5－7边形，近等径或狭长，下表皮细胞长条形；垂周壁向外隆起，平直，有明显加厚或加厚不明显，平周壁内陷，平滑具浅坑，有时具细条纹状纹饰或细小突起。气孔器散生于下表皮，均为无规则型，长度约为表皮细胞的1／4－1／3，隆起于表皮细胞或有时稍下陷。北美4种中，C．unjflora下表皮生有长的扁平状柔毛，较之其它类群更为特化，可能为一进化状态；东亚的C.udensis是一个分布较广的种类，居群间变异大，比较明显的是气孔大小的分化：西藏聂拉木和云南玉龙雪山居群气孔平均长度分别为135，6μm和110μm，而东亚其它9个居群和北美全部4种的气孔长度大致在71．6—93．7μm之间。根据以往资料和对该属种间花序形态的比较指出，东亚与北美类群之间虽然存在着分化，但其联系密切，有着历史上的渊源关系。

The leaf epidermal features of both 4 North American species and 11 populatons ofthe eastern Asian species of the genus Clintonia Raf; have been studied by LM and SEM.Cells on the upper epidermis are isodiametric in some species and slightly lolongate inothers,but on the lower side they are all lolongate. The anticlinal wall is straight,usually raised above the epidermis,with thickening conspicuous or not,while the periclinalwall is depressed,its surface is either smooth with shallow depressions or sculpturingwith fine striats,or uneven with small projections. The leaves are hypostomatic and inthe majority of species the stomata are raised above or almost level with the epidermis,only in C. udensis, the stomata sometimes slightly depressed. The anomocytic type ofstomata is uniquely observed in all species, their lengths are ranging from 7l. 6 μm to93. 7 μm,except in some populations of C. udensis,such as Nylam population from Tibetof China and Yunlong population from Yunnan Province,are respectively 135- 6 μm and110 μm. Trichomes are only occured on the abaxial surface of C. unofora,representing asone kind of long depressed hairs,this character might be an advanced statp in evolutionary process. At last,we pointed out that the close relationships between species in bothcontinents might be recalled be fore a long evolutionary histroy according to previous investigations and by comparing their inflorescence types.