Anatomy of the Dicotyledons.
About: This article is published in American Midland Naturalist.The article was published on 1950-11-01. It has received 2511 citations till now.
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TL;DR: A striking characteristic of the vascular cambium is its plasticity, it may arise in any position in any tissue except the epidermis, and a number of these possibilities may be combined in one plant either simultaneously or at different stages of growth.
Abstract: Summary
1. A striking characteristic of the vascular cambium is its plasticity. It may arise in any position in any tissue except the epidermis. It may function in a variety of ways, giving rise to xylem or phloem alone, or to both tissues. If both xylem and phloem are formed from the same cambium, they may be derived from opposite faces of the meristem or be combined as bundles or be mixed less regularly. One cambium may be succeeded by another and the method of functioning of successive cambia may vary. A number of these possibilities may be combined in one plant either simultaneously or at different stages of growth.
2. The mode of operation of the cambium in monocotyledons is so different from that of most dicotyledons, that it is unlikely that they can be homologous. It is probable that a cambium has been acquired independently in several lines of mono-cotyledonous evolution, although the virtual identity of the cambium wherever it occurs in monocotyledons is remarkable. Some dicotyledonous cambia are almost equally distinctive. To distinguish these from the usual bi-directional cambium, the term uni-directional cambium is applied to them in this account. A uni-directional cambium may be a primitive feature of the families Chenopodiaceae, Amarantaceae, and Nyctaginaceae, but essentially identical cambia have been acquired in the Styli-diaceae, the Phytolaccaceae and in several independent lines within the Compositae.
3. Another feature of the cambium is the pressure of competition between its cells. This is especially evident during the early growth of a stem, when increase of circumference is relatively great. Many cells are produced by pseudo-transverse divisions within the initial layer. These cells increase in size by intrusive growth, and many are lost. Survival has been shown to be influenced by a wide variety of factors.
4. A large number of investigations has established a pattern of variation in size of xylem elements within the tree. This reflects a similar pattern of size variation in the cambium. In broad outline this pattern is found in most trees which have been investigated, although considerably modified in timbers derived from storeyed cambia. Groups of woody plants showing other modifications of the pattern have been described.
5. The transformation of fusiform initials into ray initials and vice versa is another example of the plasticity of the cambium. The maintenance of the proportion of ray to fusiform initials characteristic of a species indicates that cambial activity is a well-co-ordinated and orderly process. The importance of a correct proportion of ray tissue among the longitudinal elements of the xylem is evident.
70 citations
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03 Oct 1991TL;DR: The Anatomy of flowering plants: an introduction to structure and development and its applications in medicine and science are presented.
Abstract: Understanding plant anatomy is not only fundamental to the study of plant systematics and palaeobotany, but is also an essential part of evolutionary biology, physiology, ecology and the rapidly expanding science of developmental genetics. This modernised new edition covers all aspects of comparative plant structure and development, arranged in a series of chapters on the stem, root, leaf, flower, pollen, seed and fruit. Internal structures are described using magnification aids from the simple hand-lens to the electron microscope. Numerous references to recent topical literature are included, and new illustrations reflect a wide range of flowering plant species. The phylogenetic context of plant names has been updated as a result of improved understanding of the relationships among flowering plants. This clearly written text is ideal for students studying a wide range of courses in botany and plant science, and is also an excellent resource for professional and amateur horticulturists.
69 citations
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TL;DR: Based on the temporal distribution, abundance, and taxonomic composition of wood floras, four phases of vegetation development are recognized through the Cretaceous to Early Tertiary of the Antarctic Peninsula: (1) Aptian to Albian communities dominated by podocarpaceous, araucarian, and minor taxodiaceous/cupressaceous conifers with rare extinct gymnosperms (Sahnioxylon) as discussed by the authors.
69 citations
Cites background from "Anatomy of the Dicotyledons."
...Identification of the fossils involved comparisons with wood descriptions (Metcalfe and Chalk, 1950; Metcalfe, 1987; Cutler and Gregory, 1998), wood anatomy atlases (Ilic, 1991), computerised databases for wood identification (e.g. OPCN wood database; Wheeler et al., 1986; Ilic, 1987; LaPasha and…...
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TL;DR: The anatomy and micromorphology of eleven species of Eugenia found in the 'restinga' of Marica, Rio de Janeiro, Brazil, were studied and compared and an analytical key based on these characteristics is presented.
68 citations
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TL;DR: This study of Hypericum perforation L. leaves and petals shows typical schizogenous translucent oil cavities that develop with a uniseriate epithelium, and both species studied exhibit secretory structures with previously undescribed anatomical features.
Abstract: SUMMARY
Hypericum species have translucent oil cavities; many species also have superficially similar black internal structures. Contradictory descriptions of both structures emerged from 19th century studies, which we review here. Our study of Hypericum perforation L. leaves and petals shows typical schizogenous translucent oil cavities that develop with a uniseriate epithelium. Black structures, in contrast, are nodules, each composed of several large cells lacking a central intercellular space and surrounded by a biseriate sheath of flattened cells. Nodule cells accumulate black, granular, but non-resinous contents. The ‘streaks’ that traverse petals are elongate tubular cavities or nodules, except for some chimerical tubes composed partly of each. Hypericum balearicum L. leaves have bulging, pustular cavities. A large cellular nodule forms first, by non-synchronous cell divisions within the leaf mesophyll, and is surrounded by a sheath of two to three flattened cell layers. The central cells then separate unevenly to form an irregular cavity into which isolated cells and clusters of cells intrude, some of which continue to divide as other cells degenerate. Little or no oil accumulates in the cavity, and the peripheral lining of cells is very irregular to flattened and empty. Both species studied exhibit secretory structures with previously undescribed anatomical features.
68 citations