Youtube williams f1 racing Youtube williams f1 racing Fiat idea adventure 2014 icarros tabela
In herbaceous dicotyledonous stems, the vascular conducting tissue (xylem and phloem) is organized into discrete strands or vascular bundles, each containing both xylem and phloem. The cells between the vascular bundles are thin-walled and often store starch. The peripheral region of cells in the stem is called the cortex; cells of the central portion make up the pith. The outermost cells of the stem compose the ep > cork cells, which together with the underlying phloem compose the bark of the tree. The major portion of the woody stem’s diameter is a cylinder of xylem (wood) that originates from a region of cell division called the vascular cambium. The water-conducting cells that make up the xylem are nonliving. The accumulated xylem often forms annual rings composed of two zones: a relatively wide zone of spring wood (made up of large cells, characteristic of rapid growth) and a narrower zone of summer wood (smaller cells). Such rings may be absent in tropical trees that grow all year round. Xylem rays, radiating like spokes of a wagon wheel, are formed in the xylem and connect with the peripheral phloem. Stems of monocotyledons are composed of numerous vascular bundles that are arranged in a seemingly scattered manner within the ground tissue. Monocot vascular bundles lack a vascular cambium, and monocot stems thus do not become woody in a manner similar to dicots.
One of the worst errors in popular media (sometimes even the documentary ones) is to portray grasslands in the Mesozoic. Arguably, writers think grass is the simplest kind of plant ever. thus, the first ever appeared on Earth. As seen above, grass are actually the most evolved plants and among the latest to become widespread on our planet. In the Dino Age, the dominant small-sized land plants were much, much more primitive: ferns, fern relatives and horsetails. These are collectively called pteridophytes and their modern descendants still make a wide portion of the undergrowth in many forests. In the Mesozoic, ferns and horsetails already made the forests' undergrowth, but also made true "prairies" where trees were absent. Only in the Mammal Age fern prairies were definitively substituted by grass prairies. But don't think ferns and horsetails were always small: in Prehistoria there were also giant horsetails and tree ferns, both deceptively similar to trees. In some places, they still live today: the 10m tall Equisetum giganteum is still growing in tropical landscapes. And tree ferns are still present in Australia and New Zealand — to the point that in the latter country they have become a national symbol, just like the kiwis. Indeed, the Land Down Under and its little neighbor are a real mine of "living fossils": not only the platypus, the kiwi, or the tuatara.
Youtube williams f1 racing Youtube williams f1 racing Youtube williams f1 racing Psilotophyta, or Psilotales (the "whisk ferns") is a grouping of nonseed plants that sometimes is considered as an order of the Class Ophioglossopsida. This order contains only two living genera, Psilotum, a small shrubby plant of the dry tropics, and Tmesipteris, anepiphyte found in Australia, New Zealand, and New Caledonia. There has long been controversy about the relationships of the Psilotophyta, with some claiming that they are ferns (Pteridophyta), and others maintaining that they are descendants of the first vascular plants (the Psilophyta of the Devonian period). Recent evidence from DNA demonstrates a much closer relationship to the ferns, and that they are closely related to the Ophioglossales, in particular.