The Zamiaceae are a family of cycads that are superficially palm or fern-like. They are divided into two subfamilies with eight genera and about 150 species in the tropical and subtropical regions of Africa and North and South America; the Zamiaceae, sometimes known as zamiads, are perennial and dioecious. They have subterranean to tall and erect unbranched, cylindrical stems, stems clad with persistent leaf bases, their leaves are pinnate, spirally arranged, interspersed with cataphylls. The leaflets are sometimes dichotomously divided; the leaflets occur with several dichotomously-branching longitudinal veins. Stomata occur either on undersurface only, their roots have small secondary roots. The coralloid roots develop at the base of the stem below the soil surface. Male and female sporophylls are spirally aggregated into determinate cones. Female sporophylls are simple, appearing peltate, with a barren stipe and an expanded and thickened lamina with 2 sessile ovules inserted on the inner surface and directed inward.
The seeds are angular, with the outer coat fleshy. They are brightly colored, with 2 cotyledons. One subfamily, the Encephalartoideae, is characterized by spirally arranged sporophylls, non-articulate leaflets and persistent leaf bases, it is represented with two genera and 40 species. As with all cycads, members of the Zamiaceae are poisonous, producing poisonous glycosides known as cycasins. Subfamily Encephalartoideae Tribe Diooeae Dioon Lindl. Tribe Encephalarteae Subtribe Encephalartinae Encephalartos Lehm. Subtribe Macrozamiinae Macrozamia Miq. Lepidozamia Lehm. Subfamily Zamioideae Tribe Ceratozamieae Ceratozamia Brongn. Tribe Zamieae Subtribe Microcycadinae Microcycas A. DC. Subtribe Zamiinae Chigua D. W. Stev. Zamia L; some classifications place the genus Bowenia in the Zamiaceae. The Cycad Pages: Zamiaceae Flora of North America New York Botanical Garden: Vascular Plant Type Catalog, some Zamiaceae genera and species
Ceratozamia is a genus of New World cycads in the family Zamiaceae. The genus contains 27 known living species and one or two fossil species. Most species are endemic to mountainous areas of Mexico, while few species extend into the mountains of Guatemala and Belize; the genus name comes from the Greek ceras, meaning horn, which refers to the paired, spreading horny projections on the male and female sporophylls of all species. Many species have limited ranges, all described species are listed as vulnerable, endangered, or critically endangered by the IUCN Red List; the whole genus is listed under CITES Appendix I / EU Annex A, CITES prohibits international trade in specimens of these species except when the purpose of the import is not commercial, for instance for scientific research. Illegal plant poaching has posed a major threat to Ceratozamia species; the plants are dioecious, with a globose or cylindrical stem dichotomously branched, that may be underground or emergent. Several species produce basal suckers.
The leaves are pinnately compound and spirally arranged. Leaf bases are deciduous but sometimes persistent; the petioles and rachis have spines, though there may be few to none. Leaflets are simple and articulate at the base, with parallel side veins and no distinct central vein. Male cones are cylindrical, upright and stalked. Female cones are stalked or sessile and have short hairs. Seeds are elliptical, with a fleshy whitish outer coat. Most species inhabit mountainous areas at 800–1000 m elevation, on sheltered slopes in moist forests; these forests range from tropical rainforests that are always wet, to pine-oak forests with alternating wet and dry seasons. There is a noticeable correlation between characteristics of species and the wetness or dryness of the habitat. Species with broad, thin leaflets live in wet habitats, species with narrow, thick leaflets live in climates with wet and dry seasons; the genus consists of 27 known species: There are several described fossil species, among them †Ceratozamia hofmannii and †Ceratozamia wrightii.
Ceratozamia wrightii is the first evidence of the genus in the fossil record, with leaf fragments of the species found in Eocene deposits on Kupreanof Island in Alaska. This would support the hypothesis that there was a subtropical climate in northern areas during the Tertiary. A fossil leaflet fragment of †Ceratozamia floersheimensis from the Rupelian stage of the Lower Oligocene has been found in marine sediments of the Bodenheim Formation in Rauenberg, Baden-Wurttemberg, Germany. Apart from Rauenberg and Flörsheim in Germany it is known from the Oligocene of Budapest and Trbovlje, Slovenia. A modern relationship exists to C. moretti, C. latifoli and C. delucana. A fossil leaf fragment of †Ceratozamia hofmannii has been recorded and described from Münzenberg near Leoben in North Bohemia, Czech Republic and dated by magnetostratigraphy and cyclostratigraphy to the last part of the early Miocene. Jones, David L.. Cycads of the World: Ancient Plants in Today's Landscape. Washington, D. C.: Smithsonian Institution Press.
ISBN 1-58834-043-0. Ceratozamia at The Cycad Pages Ceratozamia at the Gymnosperm Database
North America is a continent within the Northern Hemisphere and all within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, to the southeast by South America and the Caribbean Sea. North America covers an area of about 24,709,000 square kilometers, about 16.5% of the earth's land area and about 4.8% of its total surface. North America is the third largest continent by area, following Asia and Africa, the fourth by population after Asia and Europe. In 2013, its population was estimated at nearly 579 million people in 23 independent states, or about 7.5% of the world's population, if nearby islands are included. North America was reached by its first human populations during the last glacial period, via crossing the Bering land bridge 40,000 to 17,000 years ago; the so-called Paleo-Indian period is taken to have lasted until about 10,000 years ago. The Classic stage spans the 6th to 13th centuries.
The Pre-Columbian era ended in 1492, the transatlantic migrations—the arrival of European settlers during the Age of Discovery and the Early Modern period. Present-day cultural and ethnic patterns reflect interactions between European colonists, indigenous peoples, African slaves and their descendants. Owing to the European colonization of the Americas, most North Americans speak English, Spanish or French, their culture reflects Western traditions; the Americas are accepted as having been named after the Italian explorer Amerigo Vespucci by the German cartographers Martin Waldseemüller and Matthias Ringmann. Vespucci, who explored South America between 1497 and 1502, was the first European to suggest that the Americas were not the East Indies, but a different landmass unknown by Europeans. In 1507, Waldseemüller produced a world map, in which he placed the word "America" on the continent of South America, in the middle of what is today Brazil, he explained the rationale for the name in the accompanying book Cosmographiae Introductio:... ab Americo inventore... quasi Americi terram sive Americam.
For Waldseemüller, no one should object to the naming of the land after its discoverer. He used the Latinized version of Vespucci's name, but in its feminine form "America", following the examples of "Europa", "Asia" and "Africa". Other mapmakers extended the name America to the northern continent, In 1538, Gerard Mercator used America on his map of the world for all the Western Hemisphere; some argue that because the convention is to use the surname for naming discoveries, the derivation from "Amerigo Vespucci" could be put in question. In 1874, Thomas Belt proposed a derivation from the Amerrique mountains of Central America. Marcou corresponded with Augustus Le Plongeon, who wrote: "The name AMERICA or AMERRIQUE in the Mayan language means, a country of perpetually strong wind, or the Land of the Wind, and... the can mean... a spirit that breathes, life itself." The United Nations formally recognizes "North America" as comprising three areas: Northern America, Central America, The Caribbean.
This has been formally defined by the UN Statistics Division. The term North America maintains various definitions in accordance with context. In Canadian English, North America refers to the land mass as a whole consisting of Mexico, the United States, Canada, although it is ambiguous which other countries are included, is defined by context. In the United States of America, usage of the term may refer only to Canada and the US, sometimes includes Greenland and Mexico, as well as offshore islands. In France, Portugal, Romania and the countries of Latin America, the cognates of North America designate a subcontinent of the Americas comprising Canada, the United States, Mexico, Greenland, Saint Pierre et Miquelon, Bermuda. North America has been referred to by other names. Spanish North America was referred to as Northern America, this was the first official name given to Mexico. Geographically the North American continent has many subregions; these include cultural and geographic regions. Economic regions included those formed by trade blocs, such as the North American Trade Agreement bloc and Central American Trade Agreement.
Linguistically and culturally, the continent could be divided into Latin America. Anglo-America includes most of Northern America and Caribbean islands with English-speaking populations; the southern North American continent is composed of two regions. These are the Caribbean; the north of the continent maintains recognized regions as well. In contrast to the common definition of "North America", which encompasses the whole continent, the term "North America" is sometimes used to refer only to Mexico, the United States, Greenland; the term Northern America refers to the northern-most countries and territories of North America: the United States, Bermuda, St. Pierre and Miquelon and Greenland. Although the term does not refer to a unifie
Soil is a mixture of organic matter, gases and organisms that together support life. Earth's body of soil, called the pedosphere, has four important functions: as a medium for plant growth as a means of water storage and purification as a modifier of Earth's atmosphere as a habitat for organismsAll of these functions, in their turn, modify the soil; the pedosphere interfaces with the lithosphere, the hydrosphere, the atmosphere, the biosphere. The term pedolith, used to refer to the soil, translates to ground stone in the sense "fundamental stone". Soil consists of a solid phase of minerals and organic matter, as well as a porous phase that holds gases and water. Accordingly, soil scientists can envisage soils as a three-state system of solids and gases. Soil is a product of several factors: the influence of climate, relief and the soil's parent materials interacting over time, it continually undergoes development by way of numerous physical and biological processes, which include weathering with associated erosion.
Given its complexity and strong internal connectedness, soil ecologists regard soil as an ecosystem. Most soils have a dry bulk density between 1.1 and 1.6 g/cm3, while the soil particle density is much higher, in the range of 2.6 to 2.7 g/cm3. Little of the soil of planet Earth is older than the Pleistocene and none is older than the Cenozoic, although fossilized soils are preserved from as far back as the Archean. Soil science has two basic branches of study: pedology. Edaphology studies the influence of soils on living things. Pedology focuses on the formation and classification of soils in their natural environment. In engineering terms, soil is included in the broader concept of regolith, which includes other loose material that lies above the bedrock, as can be found on the Moon and on other celestial objects as well. Soil is commonly referred to as earth or dirt. Soil is a major component of the Earth's ecosystem; the world's ecosystems are impacted in far-reaching ways by the processes carried out in the soil, from ozone depletion and global warming to rainforest destruction and water pollution.
With respect to Earth's carbon cycle, soil is an important carbon reservoir, it is one of the most reactive to human disturbance and climate change. As the planet warms, it has been predicted that soils will add carbon dioxide to the atmosphere due to increased biological activity at higher temperatures, a positive feedback; this prediction has, been questioned on consideration of more recent knowledge on soil carbon turnover. Soil acts as an engineering medium, a habitat for soil organisms, a recycling system for nutrients and organic wastes, a regulator of water quality, a modifier of atmospheric composition, a medium for plant growth, making it a critically important provider of ecosystem services. Since soil has a tremendous range of available niches and habitats, it contains most of the Earth's genetic diversity. A gram of soil can contain billions of organisms, belonging to thousands of species microbial and in the main still unexplored. Soil has a mean prokaryotic density of 108 organisms per gram, whereas the ocean has no more than 107 procaryotic organisms per milliliter of seawater.
Organic carbon held in soil is returned to the atmosphere through the process of respiration carried out by heterotrophic organisms, but a substantial part is retained in the soil in the form of soil organic matter. Since plant roots need oxygen, ventilation is an important characteristic of soil; this ventilation can be accomplished via networks of interconnected soil pores, which absorb and hold rainwater making it available for uptake by plants. Since plants require a nearly continuous supply of water, but most regions receive sporadic rainfall, the water-holding capacity of soils is vital for plant survival. Soils can remove impurities, kill disease agents, degrade contaminants, this latter property being called natural attenuation. Soils maintain a net absorption of oxygen and methane and undergo a net release of carbon dioxide and nitrous oxide. Soils offer plants physical support, water, temperature moderation and protection from toxins. Soils provide available nutrients to plants and animals by converting dead organic matter into various nutrient forms.
A typical soil is about 50% solids, 50% voids of which half is occupied by water and half by gas. The percent soil mineral and organic content can be treated as a constant, while the percent soil water and gas content is considered variable whereby a rise in one is balanced by a reduction in the other; the pore space allows for the infiltration and movement of air and water, both of which are critical for life existing in soil. Compaction, a common problem with soils, reduces this space, preventing air and water from reaching plant roots and soil organisms. Given sufficient time, an undifferentiated soil will evolve a soil profile which consists of two or more layers, referred to as soil horizons, that differ in one or more properties such as in their texture, density, consistency, temperature and reactivity; the horizons differ in thickness and gene
Adolphe-Théodore Brongniart FRS FRSE FGS was a French botanist. He was the son of the geologist Alexandre Brongniart and grandson of the architect, Alexandre-Théodore Brongniart. Brongniart's pioneering work on the relationships between extinct and existing plants has earned him the title of father of paleobotany, his major work on plant fossils was his Histoire des végétaux fossiles. He wrote his dissertation on the Buckthorn family, an extant family of flowering plants, worked at the Muséum national d'Histoire naturelle in Paris until his death. In 1851, he was elected a foreign member of the Royal Swedish Academy of Sciences; this botanist is denoted by the author abbreviation Brongn. When citing a botanical name. Brongniart was a prolific writer of books and memoirs; as early as 1822 he published a paper on the distribution of fossil plants. This was followed by several papers chiefly bearing upon the relation between extinct and existing forms - a line of research which culminated in the publication of the Histoire des vegetaux fossiles, which has earned for him the title of "father of paleobotany."
This classification arranged fossil plants with their nearest living allies. It is of especial botanical interest, because, in accordance with Robert Brown's discoveries of the fundamental difference between Gymnosperms and Angiosperms, the Cycadeae and Coniferae were placed in the new group the gymnosperms. In Brongniart's Histoire des végétaux fossiles attention was directed to the succession of forms in the various geological periods, with the important result that in the Palaeozoic period the Pteridophyta are found to predominate, but the Histoire itself was not completed. Apart from his more comprehensive works, his most important palaeontological contributions are his observations on the structure of the treelike lycopod, Sigillaria, an extinct plant related to the living club mosses, his researches on fossil seeds, of which a full account was published posthumously in 1880, he was active in many branches of botany, including anatomy and the taxonomy of seed-producing plants. Among his achievements in this direction, the most notable is the treatise Sur la génération et le développement de l'embryon des Phanérogames, remarkable for the first account of any value of the development and structure of Pollen, along with the confirmation of Giovanni Battista Amici's 1823 discovery of the pollen-tube, the confirmation of Robert Brown's views as to the structure of the unimpregnated ovule, showing how nearly Brongniart anticipated Amici's subsequent discovery of the entrance of the pollen-tube into the micropyle, fertilizing the female cell, which develops into the embryo.
Of his anatomical works, those of the greatest value are the "Recherches sur la structure et les fonctions des feuilles", the Nouvelles recherches sur 1'épiderme, in which, among other important observations, the discovery of the cuticle is recorded. His systematic work is represented by a large number of papers and monographs, many of which relate to the flora of New Caledonia. In addition to his scientific and professorial labours, Brongniart held various important official posts in connection with the department of education, interested himself in agricultural and horticultural matters. With Jean Victoire Audouin and Jean-Baptiste Dumas, his future brothers-in-law, Brongniart founded the Annales des Sciences Naturelles, a peer-reviewed journal, in 1824, he founded the Société Botanique de France in 1854, was its first president. This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed.. "Brongniart, Adolphe Théodore". Encyclopædia Britannica. Cambridge University Press.
Books by and about Brongniart on WorldCat
A leaf is an organ of a vascular plant and is the principal lateral appendage of the stem. The leaves and stem together form the shoot. Leaves are collectively referred to as foliage, as in "autumn foliage". A leaf is a thin, dorsiventrally flattened organ borne above ground and specialized for photosynthesis. In most leaves, the primary photosynthetic tissue, the palisade mesophyll, is located on the upper side of the blade or lamina of the leaf but in some species, including the mature foliage of Eucalyptus, palisade mesophyll is present on both sides and the leaves are said to be isobilateral. Most leaves have distinct upper surface and lower surface that differ in colour, the number of stomata, the amount and structure of epicuticular wax and other features. Leaves can have many different shapes and textures; the broad, flat leaves with complex venation of flowering plants are known as megaphylls and the species that bear them, the majority, as broad-leaved or megaphyllous plants. In the clubmosses, with different evolutionary origins, the leaves are simple and are known as microphylls.
Some leaves, such as bulb scales, are not above ground. In many aquatic species the leaves are submerged in water. Succulent plants have thick juicy leaves, but some leaves are without major photosynthetic function and may be dead at maturity, as in some cataphylls and spines. Furthermore, several kinds of leaf-like structures found in vascular plants are not homologous with them. Examples include flattened plant stems called phylloclades and cladodes, flattened leaf stems called phyllodes which differ from leaves both in their structure and origin; some structures of non-vascular plants function much like leaves. Examples include the phyllids of liverworts. Leaves are the most important organs of most vascular plants. Green plants are autotrophic, meaning that they do not obtain food from other living things but instead create their own food by photosynthesis, they capture the energy in sunlight and use it to make simple sugars, such as glucose and sucrose, from carbon dioxide and water. The sugars are stored as starch, further processed by chemical synthesis into more complex organic molecules such as proteins or cellulose, the basic structural material in plant cell walls, or metabolised by cellular respiration to provide chemical energy to run cellular processes.
The leaves draw water from the ground in the transpiration stream through a vascular conducting system known as xylem and obtain carbon dioxide from the atmosphere by diffusion through openings called stomata in the outer covering layer of the leaf, while leaves are orientated to maximise their exposure to sunlight. Once sugar has been synthesized, it needs to be transported to areas of active growth such as the plant shoots and roots. Vascular plants transport sucrose in a special tissue called the phloem; the phloem and xylem are parallel to each other but the transport of materials is in opposite directions. Within the leaf these vascular systems branch to form veins which supply as much of the leaf as possible, ensuring that cells carrying out photosynthesis are close to the transportation system. Leaves are broad and thin, thereby maximising the surface area directly exposed to light and enabling the light to penetrate the tissues and reach the chloroplasts, thus promoting photosynthesis.
They are arranged on the plant so as to expose their surfaces to light as efficiently as possible without shading each other, but there are many exceptions and complications. For instance plants adapted to windy conditions may have pendent leaves, such as in many willows and eucalyptss; the flat, or laminar, shape maximises thermal contact with the surrounding air, promoting cooling. Functionally, in addition to carrying out photosynthesis, the leaf is the principal site of transpiration, providing the energy required to draw the transpiration stream up from the roots, guttation. Many gymnosperms have thin needle-like or scale-like leaves that can be advantageous in cold climates with frequent snow and frost; these are interpreted as reduced from megaphyllous leaves of their Devonian ancestors. Some leaf forms are adapted to modulate the amount of light they absorb to avoid or mitigate excessive heat, ultraviolet damage, or desiccation, or to sacrifice light-absorption efficiency in favour of protection from herbivory.
For xerophytes the major constraint drought. Some window plants such as Fenestraria species and some Haworthia species such as Haworthia tesselata and Haworthia truncata are examples of xerophytes. and Bulbine mesembryanthemoides. Leaves function to store chemical energy and water and may become specialised organs serving other functions, such as tendrils of peas and other legumes, the protective spines of cacti and the insect traps in carnivorous plants such as Nepenthes and Sarracenia. Leaves are the fundamental structural units from which cones are constructed in gymnosperms and from which flowers are constructed in flowering plants; the internal organisation of most kinds of leaves has evolved to maximise exposure of the photosynthetic organelles, the chloroplasts, to light and to increase the absorption of carbon dioxide while at the same time controlling water loss. Their surfaces are waterproofed by the plant cuticle and gas exchange between the mesophyll cells and the atmosphere is controlled by minute openings called stomata which open or close to regulate the rate exchange of carbon dioxide and water vapour into
Lepidozamia is a genus of two species of cycad, both endemic to Australia. The name, derived from the Greek word lepidos, meaning scaly, refers to the scale-like structure of the stem and leaf bases, they are native to rainforest climates in eastern New South Wales. They have a chromosome number of 2n = 18. A specimen of L. hopei is known as the tallest living cycad at 17.5 m tall. These cycads are unbranched and with persistent leaf bases, they are cultivated as ornamental plants and are cold hardy. The Cycad Pages: Lepidozamia Whitelock, L. M. 2002. The Cycads. Portland, Oregon: The Timber Press. 2002