Evolutionary study of a unique morphology, anisocotyly of Gesneriaceas

对大链霉（Streptocarpus grandis）、马田单霉（Monophyllaea horsfieldii）和单霉（m.s ulularis singularis）的单根性进行了个体发育和解剖研究，并与茎生种S. kirkii和莲座种S. rexii的个体发育进行了比较。在所有被调查的物种中，种子脱落阶段的胚胎由一个下胚轴和两个等大小的子叶组成，缺乏根和茎尖。在萌发过程中，细胞分裂和随后的细胞增大发生在下胚轴和子叶。下胚轴很快从其远端尖端产生主根，包括残柄附着点的表面细胞和下表面细胞。在子叶中，细胞的扩大和分化基本发生，在基部留下小的分生细胞。这些小细胞在一个子叶中产生基生分生组织，这有助于增加子叶，但在另一个子叶中没有。由于一个子叶的基生分生组织长期活跃，形成了明显的各向异性，即两个子叶之间的大小差异。沟槽分生组织，后来分化成一个花序，当子叶变得明显不相等时，在茎尖处产生。在单叶植物和莲座植物中直接分化为花序分生组织，而在茎生植物中分化为营养枝尖。根据形态发生资料，讨论了单叶链藻独特生长的进化过程。

The monophylly of Streptocarpus grandis, Monophyllaea horsfieldii, and M. singularis was examined ontogenetically and anatomically, and compared with the ontogenesis of the caulescent species, S. kirkii, and of rosulate species, S. rexii. In all species examined, the embryo in the seed shedding stage is composed of a hypocotyl and two equal-sized cotyledons, lacking root and shoot apices. During germination, cell division and subsequent cell enlargement occur in the hypocotyl and cotyledons. The hypocotyl soon produces a primary root from its distal tip, involving surface and subsurface cells at the attaching point of the suspensor remnant. In the cotyledons, cell enlargement and differentiation occur basipetally, leaving small meristematic cells at the bases. These small cells give rise to the basal meristem in one cotyledon, which contributes to an accrescent cotyledon, but do not in the other cotyledon. Due to long-erm activity of the basal meristem in one cotyledon, the apparent anisocotyly, that is, the size difference between two cotyledons is established. The groove meristem, which later differentiates into an inflorescence, arises in place of shoot apices when the cotyledons become apparently unequal. It later exhibits a tunica-corpus like configuration and differentiates directly into inflorescence meristem in monophyllous and rosulate species, but into vegetative shoot-apex in caulescent species. The evolution of the unique growth of one-leaved Streptocarpus is discussed on the basis of the morphogenetic data.