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Psilotum Complanatum
''Psilotum complanatum'', the flatfork fern, is a rare herbaceous epiphytic fern ally in the genus ''Psilotum''. There is some evidence that it might be a true fern that has lost some typically fern-like characteristics. Morphologically, the plant is simple, lacking leaves and roots, and having hanging stems with dichotomous branching, which lack developed leaves but have minute scales. The stems and branches have protostele, with a triangular-shaped core of xylem. The scales are arranged in two rows along the flat stems and branches. The stems are broadly triangular in cross section and 5 mm wide. The branches are 1.5 to 2 mm wide. ''P. complanatum'' grows 10 to 75 cm long and stems branch in pairs a number of times up their length and are covered with brownish colored hair-like rhizoids. Small stalks end with simple sporangia from the axils of minute bifid, rounded sporophylls. Bean shaped, monolete spores are produced. The spores germinate best in a dark enviro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Olof Swartz
Olof Peter Swartz (21 September 1760 – 19 September 1818) was a Swedish botanist and taxonomist. He is best known for his taxonomic work and studies into pteridophytes. Biography Olof Swartz attended the University of Uppsala where he studied under Carl Linnaeus the Younger (1741–1783) and received his doctorate in 1781. He first traveled in 1780 to Lapland in the company of several other botanists. In 1783 he sailed for North America and the West Indies, primarily in the area of Jamaica and Hispaniola, to collect botanical specimens. His botanical collection, of an impressive 6000 specimens, is now held by the Swedish Museum of Natural History, as part of the Regnellian herbarium. By 1786 he left for London to prepare his collection. There he met naturalist Joseph Banks (1743–1820), who was impressed with his knowledge of Botany. He was offered a position with the British East India Company as a travelling physician, but turned it down, and returned to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epiphytic
An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphytes grow are called phorophytes. Epiphytes take part in nutrient cycles and add to both the diversity and biomass of the ecosystem in which they occur, like any other organism. They are an important source of food for many species. Typically, the older parts of a plant will have more epiphytes growing on them. Epiphytes differ from parasites in that they grow on other plants for physical support and do not necessarily affect the host negatively. An organism that grows on another organism that is not a plant may be called an epibiont. Epiphytes are usually found in the temperate zone (e.g., many mosses, liverworts, lichens, and algae) or in the tropics (e.g., many ferns, cacti, orchids, and bromeliads). Epiphyte species make good houseplants due to their minimal water ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fern Ally
Fern allies are a diverse group of seedless vascular plants that are not true ferns. Like ferns, a fern ally disperses by shedding spores to initiate an alternation of generations. Classification Originally, three or four groups of plants were considered to be fern allies. In various classification schemes, these may be grouped as classes or divisions within the plant kingdom. Fern allies and ferns were sometimes grouped together as division Pteridophyta. Another traditional classification scheme of living plants is as follows (here, the first three classes are the "fern allies"): *Kingdom: Plantae **Division Tracheophyta (vascular plants) ***Class Lycopsida, clubmosses and related plants (fern-allies) ***Class Sphenopsida or Equisetopsida, horsetails and scouring-rushes (fern-allies) ***Class Psilopsida, whisk ferns (fern-allies) ***Class Filices or Pteropsida, true ferns ***Class Spermatopsida (or sometimes as several different classes of seed-bearing plants) More recen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fern
A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except the lycopods, and differ from mosses and other bryophytes by being vascular, i.e., having specialized tissues that conduct water and nutrients and in having life cycles in which the branched sporophyte is the dominant phase. Ferns have complex leaves called megaphylls, that are more complex than the microphylls of clubmosses. Most ferns are leptosporangiate ferns. They produce coiled fiddleheads that uncoil and expand into fronds. The group includes about 10,560 known extant species. Ferns are defined here in the broad sense, being all of the Polypodiopsida, comprising both the leptosporangiate (Polypodiidae) and eusporangiate ferns, the latter group including horsetails, whisk ferns, marattioid ferns, and ophioglossoid ferns. Ferns first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dichotomous Branching
This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary of leaf morphology. For other related terms, see Glossary of phytopathology, Glossary of lichen terms, and List of Latin and Greek words commonly used in systematic names. A B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protostele
In a vascular plant, the stele is the central part of the root or stem containing the tissues derived from the procambium. These include vascular tissue, in some cases ground tissue (pith) and a pericycle, which, if present, defines the outermost boundary of the stele. Outside the stele lies the endodermis, which is the innermost cell layer of the cortex. The concept of the stele was developed in the late 19th century by French botanists P. E. L. van Tieghem and H. Doultion as a model for understanding the relationship between the shoot and root, and for discussing the evolution of vascular plant morphology. Now, at the beginning of the 21st century, plant molecular biologists are coming to understand the genetics and developmental pathways that govern tissue patterns in the stele. Moreover, physiologists are examining how the anatomy (sizes and shapes) of different steles affect the function of organs. Protostele The earliest vascular plants had stems with a central core of v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xylem
Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived from the Ancient Greek word (''xylon''), meaning "wood"; the best-known xylem tissue is wood, though it is found throughout a plant. The term was introduced by Carl Nägeli in 1858. Structure The most distinctive xylem cells are the long tracheary elements that transport water. Tracheids and vessel elements are distinguished by their shape; vessel elements are shorter, and are connected together into long tubes that are called ''vessels''. Xylem also contains two other type of cells: parenchyma and fibers. Xylem can be found: * in vascular bundles, present in non-woody plants and non-woody parts of woody plants * in secondary xylem, laid down by a meristem called the vascular cambium in woody plants * as part of a stelar arrangement n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhizoid
Rhizoids are protuberances that extend from the lower epidermal cells of bryophytes and algae. They are similar in structure and function to the root hairs of vascular land plants. Similar structures are formed by some fungi. Rhizoids may be unicellular or multicellular. Evolutionary development Plants originated in aquatic environments and gradually migrated to land during their long course of evolution. In water or near it, plants could absorb water from their surroundings, with no need for any special absorbing organ or tissue. Additionally, in the primitive states of plant development, tissue differentiation and division of labor was minimal, thus specialized water absorbing tissue was not required. The development of specialized tissues to absorb water efficiently and anchor themselves to the ground enabled the spread of plants to the land. Description Rhizoids absorb water mainly by capillary action, in which water moves up between threads of rhizoids and not through ea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sporangia
A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cycle. Sporangia can produce spores by mitosis, but in nearly all land plants and many fungi, sporangia are the site of meiosis and produce genetically distinct haploid spores. Fungi In some phyla of fungi, the sporangium plays a role in asexual reproduction, and may play an indirect role in sexual reproduction. The sporangium forms on the sporangiophore and contains haploid nuclei and cytoplasm. Spores are formed in the sporangiophore by encasing each haploid nucleus and cytoplasm in a tough outer membrane. During asexual reproduction, these spores are dispersed via wind and germinate into haploid hyphae. Although sexual reproduction in fungi varies between phyla, for some fungi the sporangium plays an indirect role in sexual reproducti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bifid , a congenital abnormality of the human anatomy
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Bifid refers to something that is split or cleft into two parts. It may refer to: * Bifid, a variation in the P wave, R wave, or T wave in an echocardiogram in which a wave which usually has a single peak instead has two separate peaks * Bifid cipher, a type of cipher in cryptography * Bifid penis * Bifid nose, a split nose that can even look like two noses; a fairly common trait in some dog varieties, especially the and its descendants * Bifid rib A bifid rib is a congenital abnormality of the rib cage and associated muscles and nerves which occurs in about 1.2% of humans. Bifid ribs occur in up to 8.4% of Samoans. The sternal end of the rib is cleaved into two. It is usually unilateral. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sporophyll
A sporophyll is a leaf that bears sporangia. Both microphylls and megaphylls can be sporophylls. In heterosporous plants, sporophylls (whether they are microphylls or megaphylls) bear either megasporangia and thus are called megasporophylls, or microsporangia and are called microsporophylls. The overlap of the prefixes and roots makes these terms a particularly confusing subset of botanical nomenclature. Sporophylls vary greatly in appearance and structure, and may or may not look similar to sterile leaves. Plants that produce sporophylls include: ''Alaria esculenta'', a brown alga which shows sporophylls attached near the base of the alga.Dickson, Carola I. 1963. ''British Seaweeds''. The Kew Series. Lycophytes, where sporophylls may be aggregated into strobili (''Selaginella'' and some ''Lycopodium'' and related genera) or distributed singly among sterile leaves (''Huperzia''). Sporangia are borne in the axil or on the adaxial surface of the sporophyll. In heterosporous members ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spore
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, fungi and protozoa. Bacterial spores are not part of a sexual cycle, but are resistant structures used for survival under unfavourable conditions. Myxozoan spores release amoeboid infectious germs ("amoebulae") into their hosts for parasitic infection, but also reproduce within the hosts through the pairing of two nuclei within the plasmodium, which develops from the amoebula. In plants, spores are usually haploid and unicellular and are produced by meiosis in the sporangium of a diploid sporophyte. Under favourable conditions the spore can develop into a new organism using mitotic division, producing a multicellular gametophyte, which eventually goes on to produce gametes. Two gametes fuse to form a zygote which develops into a new s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
