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Megasporogenesis, formation of the megaspores in the megasporangium (nucellus) by meiosis; Megagametogenesis; development of the megaspore(s) into the megagametophyte(s) which contains the gametes. [2] In gymnosperms and most flowering plants, only one of the four megaspores is functional at maturity, and the other three soon degenerate.
The defining characteristics of the Lepidodendrales are their secondary xylem, extensive periderm development, three-zoned cortex, rootlike appendages known as stigmarian rootlets arranged in a spiralling pattern, and megasporangium each containing a single functional megaspore that germinates inside the sporangium. Many of these different ...
A sporangium (from Late Latin, from Ancient Greek σπορά (sporá) 'seed' and ἀγγεῖον (angeîon) 'vessel'); pl.: sporangia) [1] is an enclosure in which spores are formed. [2]
Areas 1 and 2 receive most of their input from area 3. There are also pathways for proprioception (via the cerebellum), and motor control (via Brodmann area 4). See also: S2 Secondary somatosensory cortex. The human eye is the first element of a sensory system: in this case, vision, for the visual system.
Megaspores, also called macrospores, are a type of spore that is present in heterosporous plants. These plants have two spore types, megaspores and microspores. Generally speaking, the megaspore, or large spore, germinates into a female gametophyte, which produces egg cells.
The area of the visual cortex that receives the sensory input from the lateral geniculate nucleus is the primary visual cortex, also known as visual area 1 , Brodmann area 17, or the striate cortex. The extrastriate areas consist of visual areas 2, 3, 4, and 5 (also known as V2, V3, V4, and V5, or Brodmann area 18 and all Brodmann area 19). [1]
An additional set of neurons, known as the koniocellular layers, are found ventral to each of the magnocellular and parvocellular layers. [3]: 227ff [4] This layering is variable between primate species, and extra leafleting is variable within species. The average volume of each LGN in an adult human is about 118mm. (This is the same volume as ...
The visual system is the physiological basis of visual perception (the ability to detect and process light).The system detects, transduces and interprets information concerning light within the visible range to construct an image and build a mental model of the surrounding environment.