Aperture (botany) pollen grain. Aperture (botany) Apertures are areas on the walls of a pollen grain, where the wall is thinner and/or softer. For germination it is necessary that the pollen tube can reach out from the inside of the pollen grain and transport the sperm to the egg deep down in the pistil. The apertures are the places where the pollen tube is able to break through the (elsewhere very tough) pollen wall. The number and configuration of apertures are often very exactly characteristic of different groups of plants. The biggest class of plant species, the Eudicots, usually have three apertures
Decay theory that older memories (in long-term memory) are often more resistant to shocks or physical attacks on the brain. It is also thought that the passage of time alone cannot cause forgetting, and that decay theory must also take into account some processes that occur as more time passes. The term "decay theory" was first coined by Edward Thorndike in his book "The Psychology of Learning" in 1914. This simply states that if a person does not access and use the memory representation they have formed the memory trace will fade or decay over time. This theory was based on the