星叶草叶脉序的形态学及其系统学意义

在星叶草叶二叉分枝脉序中，网结脉中2条完全汇合叶脉与靠近脉中完全分离叶脉间未发现任 何形式的维管束汇合的中间类型，相反观察到了网结脉中不同程度的连接脉退化的痕迹，因此网结脉不可能由靠近脉形成；盲脉的出现与齿的退化、网结脉中连接脉的间断及非网结脉由分枝处间断等相关；上述事实表明星叶草叶的二叉分枝脉序应为一减化性状。

THE MORPHOLOGY OF THE DICHOTOMOUS LEAF VENATION OF CIRCAEASTER AGRESTIS AND ITS SYSTEMATIC IMPLICATION

Observations on the dichotomous leaf venation of Circaeaster agrestis found no intermediate forms of the fusion of vascular bundles between the two completely fused commis-sural veins of anastomoses and the two separate approximate veins, but found different degrees of the vestige of commissural veins . The fact indicates the impossibility of the formation of anastomoses from approximate veins. The occurrence of blind veins is related to the degeneration of teeth, the interruption of the commissural veins and the interruption of non-anastomosous veins at the branching point . Therefore, we considered the dichotomous leaf venation of this species as a reduced characteristic.