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Publisher Summary This chapter discusses the morphology and anatomy of monocotyledons. The ritualistic presentation of a transverse section of the internode of a corn stem to illustrate the “typical monocotyledonous” stem is an exercise that features in most courses of elementary biology and along with it goes the dogma of the “scattered” arrangement of vascular bundles that distinguishes monocotyledons from herbaceous dicotyledons. The common development of aerenchymatous tissues, associated with the marked tendency of monocotyledons to occupy wet habitats, has led to the supposition that monocotyledons are the descendants of aquatic dicotyledonous ancestors. This overlooks the fact that the aquatic monocotyledons are specialized in their vegetative habitat, and it is difficult to derive rhizomatous, woody, and particularly arborescent forms from them. The growth-limiting characteristics of plants without secondary vascular tissues are discussed. These limitations involve a restriction on branching of distal parts, problems of mechanical stability, and methods of maintaining adequate pathways for long-distance transport through the base of a plant that has no secondary method of supplementing its vascular supply. A common arrangement of the stomatal complex in monocotyledons involves a pair of lateral subsidiary cells. The subsidiary cells are recognized by their thin walls. A convenient term to describe this type is “paracytic.” |
