Comparative morphology of Selaginella rhizophore

对热带3种大型卷柏属植物的根状茎进行了形态发生研究。细卷柏（Selaginella delicatula）、尾卷柏（s.a caudata）和平卷柏（s.a plana）的根茎在主茎的分枝处外生。在尾茎中，它们是在第二个最年轻分支的交界处开始的。根茎顶端分生组织有一个四面体的顶端细胞，无帽。根状茎通常是三到四次分叉，在山楂和plana中是四到五次分叉。在s.d delicatula中，根状茎的二分分支涉及在失去一个原有的根尖细胞后形成两个新的根尖细胞。一对根是在根茎末梢的真皮层以下的内部细胞内源性形成的。根状茎是一个自主分支、无叶、无帽的轴，这一发现使我们认为卷柏的根状茎和鳞翅果的根状茎一样，是与茎和根协调的基本轴器官。裸盖科植物是现存维管植物中组织最简单的植物，由不规则分枝的地下“根茎”和简单或二分枝的多叶气生芽组成。它们在整个生命周期中都缺乏根基。裸盖科植物的地下“根茎”是一个神秘的器官。虽然“根状茎”有不封顶的顶端分生组织，它明显不同于一个真正的茎缺乏附属叶（和根），并且只产生根状体。根茎被认为是维管植物的基本器官之一。将其与非茎轴器官，如卷柏（Selaginella rhizophore）、鳞翅果（lepidendendrid，包括lsoetes）的根状体和一些早期化石维管植物的微分化组织的地下轴进行了比较。

A morphogenetic investigation was made of the rhizophore of three large-sized tropical Selaginella species. The rhizophores of Selaginella delicatula, S.caudata, S. plana arise exogenously at the points of branching of the main stems. In S.caudata they are initiated at the junction of the second youngest branching. The rhizophore apical meristem has a tetrahedral apical cell and is capless. The rhizophores are usually three or four times dichotomously branched in S.delicatula and S.plana and four or five times in S.caudata. In S.delicatula, dichotomous branching of the rhizophore involves formation of two new apical cells subsequent to loss of an original apical cell. A pair of roots is formed endogenously from inner cells below the dermal layer at the apex of ultimate rhizophore branches. The finding that the rhizophore is an autonomously branched, leafless, and capless axis leads us to argue that Selaginella rhizophores, like lepidodendrid rhizomorphs, are fundamental axial organs that coordinate with the stem and root.The plants of Psilotaceae are the most simply organized among living vascular plants and consist of irregularly branched subterranean "rhizome" and simple or dichotomously branched, leafy aerial shoots. They lack roots throughout the life cycle. The subterranean "rhizome" of Psilotaceae is an enigmatic organ. While the "rhizome" has uncapped apical meristem, it differs distinctly from a genuine stem by lacking appendicular leaves(and also roots), and bearing only rhizoids. The "rhizome" is considered to be one of the fundamental organs of vascular plants. It is compared with non-stem axial organs such as the Selaginella rhizophore, the lepidodendrid (including lsoetes) rhizomorphs, and the subterranean axes of some early fossil vascular plants of subtly differentiated organization.