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The epidermis is a layer of cells that cover the plant body, including the stems, leaves, flowers and fruits, that protects the plant from the outside world. In old stems the epidermal layer, cortex, and primary phloem become separated from the inner tissues by thicker formations of cork.
Non-vascular plants , with their different evolutionary background, tend to have separate terminology. Although plant morphology (the external form) is integrated with plant anatomy (the internal form), the former became the basis of the taxonomic description of plants that exists today, due to the few tools required to observe. [2] [3]
The plant morphologist goes further, and discovers that the spines of cactus also share the same basic structure and development as leaves in other plants, and therefore cactus spines are homologous to leaves as well. This aspect of plant morphology overlaps with the study of plant evolution and paleobotany.
Dicotyledon plantlet Young castor oil plant showing its prominent two embryonic leaves (), which differ from the adult leaves. The dicotyledons, also known as dicots (or, more rarely, dicotyls), [2] are one of the two groups into which all the flowering plants (angiosperms) were formerly divided.
These adaptations enable it to occupy niches too harsh for vascular plants or mosses, reducing competition in these environments. [17] The podetia show a high degree of variability, ranging from entirely decorticate surfaces to densely squamulose ones, allowing the lichen to adapt to a wide range of environmental conditions and substrate types.
Prickles on a blackberry branch. In plant morphology, thorns, spines, and prickles, and in general spinose structures (sometimes called spinose teeth or spinose apical processes), are hard, rigid extensions or modifications of leaves, roots, stems, or buds with sharp, stiff ends, and generally serve the same function: physically defending plants against herbivory.
The thallus is also heteromerous (parts that are different in quality and number) and fully corticated (has a cortex and bark). Many of the Umbilicaria species are characterized by a veined or rugose thalline surface.
In embryophytes (land plants) the zygote will instead give rise to a multicellular sporophyte. [20] [21] Except from land plants, retention of the zygote is only known from some species in one group of green algae; the coleochaetes. In these species the zygote is corticated by a layer of sterile gametophytic cells.