Gnetophyta Welwitschia mirabilis male cones Ephedra distachya (male flowers) Ephedra distachya (female plant in bloom) Gnetum gnemon male Gnetum gnemon female Ecology and morphology The three genera of the gnetophytes are highly specialized to their respective environments, making it difficult to identify homologous characters. The three extant genera of gnetophytes, a "bizarre and enigmatic" trio, are likely aberrant members of the group, which was diverse and dominant in the Tertiary. Some synapomorphies of the gnetophytes include enveloping bracts around the ovules and microsporangia, and a micropylar projection of the outer membrane of the ovule that produces a pollination droplet. Gnetum species are mostly woody climbers in tropical forests. Welwitschia comprises only one species, Welwitschia mirabilis. Classification Anthophyte hypothesis Gnetifer hypothesis Gnepine hypothesis Gnetophyte-sister hypothesis References Other Sources:
Classification APG III Un article de Wikipédia, l'encyclopédie libre. La classification APG III (2009), ou classification phylogénétique, est la troisième version de classification botanique des angiospermes établie par l'Angiosperms Phylogeny Group. C'est la classification botanique la plus importante aujourd'hui. Elle est une modification de la classification APG II (2003). Comme la classification APG et la classification APG II, cette classification est construite à la base de deux gènes chloroplastiques et un gène nucléaire de ribosome, mais ces données sont complétées dans quelques cas par d'autres données. APG III selon Mark W. En octobre 2009, alors que l'Angiosperm Phylogeny Group publiait APG III, deux des membres de l'APG, Mark W. Ce document semble actuellement être assez suivi sur internet. Tropicos (Rosaceae y est placé dans Rosanae. Classification résumée[modifier | modifier le code] Classification détaillée (avec toutes les familles)[modifier | modifier le code] Légende:
How a Photographer Created Images of Fireworks Unlike Any You've Ever Seen - Megan Garber A photographer's experiment puts explosions in new light. A spaceship? A sea creature? A spunky chapeau? Nope: fireworks. Earlier this month, David Johnson found himself at the International Fireworks Show in Ottawa, Canada. The resulting images, which I first saw on the blog This Is Colossal, are mesmerizing. As Johnson later told me of his method: The way I captured the photos was actually pretty simple... it just required good timing. It does! A dandelion: A group of dandelions: A sunflower: Thistles: Spores: Viruses: An armored insect: You can see more over at Johnson's website, here. Via Steve Silberman and This Is Colossal.
Anthophyta The anthophytes were thought to be a clade comprising plants bearing flower-like structures. The group contained the angiosperms - the extant flowering plants - as well as the Gnetales and the extinct Bennettitales. It also includes such plants as roses, tulips, and common plants found to have flower structures. Detailed morphological and molecular studies have shown that the group is not actually monophyletic, with proposed floral homologies of the gnetophytes and the angiosperms having evolved in parallel. This makes it easier to reconcile molecular clock data that suggests that the angiosperms diverged from the gymnosperms around 300 million years ago. Some more recent studies have used the word anthophyte to describe a group which includes the angiosperms and a variety of fossils (glossopterids, Pentoxylon, Bennettitales, and Caytonia), but not the Gnetales. Phylogeny of anthophytes and gymnosperms, from 
Botanical Nomenclature Nomenclature Nomenclature refers to the naming of things. Botanical nomenclature is (surprise) about naming plants. Bear in mind that plant names refer to abstract entities - the collection of all plants (past, present, and future) that belong to the same group. As you will recall, taxonomy is about grouping. Botanical nomenclature is about applying names to taxonomic groups. Scientific names of plants reflect the taxonomic group to which the plant belongs. Scientific names are never misleading. Pronunciation. Taxonomy refers to forming groups. If people are going to communicate around the world, there needs to be an internationally accepted system of nomenclature. Towards an International Code Pre-Linnaean Practices 1) Names were formed like Latin words. 2) Once a name had been attached to a plant group, it should not be given another name. 3) When commenting on how a name was to be interpreted, one should list the names of others that had used it. Other Codes Agreement, at last 2. Form.
A small (but glorious) world: The best microscope images of 2012 Most people know Nikon as a purveyor of pro and consumer-grade digital cameras. But the company's expertise with optics bleeds over into related markets—it's one of the science community's major suppliers of microscopes. And each year the company asks the community to send it some of their favorite images of tiny objects. A panel of scientists and journalists have chosen the best of this past year's submissions, which Nikon has placed on its Small World site. We've gone through and picked out some of our favorite images from this year, and Nikon provided some high-resolution versions. The grand prize winner at top highlights the blood vessels as they form in the brain of a zebrafish. Confocals only capture light from a single plane of focus, so each individual image is like an optical slice through the tissue. Lynx spiders are a very successful genus, with members found on every continent. Cancer's an ugly disease, but damn, this image of a cancerous cell looks good.
Cycad Cycads are gymnosperms (naked seeded), meaning their unfertilized seeds are open to the air to be directly fertilized by pollination, as contrasted with angiosperms, which have enclosed seeds with more complex fertilization arrangements. Cycads have very specialized pollinators, usually a specific species of beetle. They have been reported to fix nitrogen in association with a cyanobacterium living in the roots. These blue-green algae produce a neurotoxin called BMAA that is found in the seeds of cycads. Origins Taxonomy The number of species in the clade is low compared to the number in most other plant phyla. The number of described cycad species has doubled in the past 25 years, mostly due to improved sampling and further exploration. Suborder Cycadineae Family Cycadaceae Subfamily Cycadoideae Cycas. Suborder Zamiineae Family Stangeriaceae Subfamily Stangerioideae Stangeria. Subfamily Bowenioideae Bowenia. Family Zamiaceae Subfamily Encephalartoideae Tribe Diooeae Encephalartos.
Forme des cristaux de neige et origine des avalanches Forme des cristaux de neige et origine des avalanches Étienne REYSSATClaire TAMAIN Introduction : Les premières études des cristaux de neige se bornaient à décrire les différentes formes qu'ils pouvaient prendre. Aujourd'hui, on en fait une approche plus scientifique, avec des moyens plus évolués, dans le but de comprendre leur formation et leur évolution. De plus, l'étude des cristaux n'est plus une fin en soi, mais elle a notamment pour objectif d'expliquer comment les transformations des cristaux peut aboutir au phénomène d'avalanche. I. Johannes Kepler : En 1611, Kepler publie un petit traité qui est une des premières approches scientifiques de l'étude des cristaux de neige. René Descartes : Descartes est le premier, en 1635, à décrire précisément plusieurs formes de cristaux de neige. Robert Hooke : En 1665, l'invention récente du microscope permet à Hooke de réaliser des observations encore plus précises. Wilson A. Bentley était un fermier et un photographe Américain. Ukichiro Nakaya b.
Pinophyta Although the total number of species is relatively small, conifers are of immense ecological importance. They are the dominant plants over huge areas of land, most notably the boreal forests of the northern hemisphere, but also in similar cool climates in mountains further south. Boreal conifers have many wintertime adaptations. The narrow conical shape of northern conifers, and their downward-drooping limbs, help them shed snow. They are also of great economic value, primarily for timber and paper production; the wood of conifers is known as softwood. Conifer is a Latin word, a compound of conus (cone) and ferre (to bear), meaning "the one that bears (a) cone(s)". Evolution The earliest conifers in the fossil record date to the late Carboniferous (Pennsylvanian) period (about 300 million years ago), possibly arising from Cordaites, a seed-bearing plant with cone-like fertile structures. Taxonomy and naming Morphology Foliage Reproduction