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As more water evaporates, air bubbles form in the cells causing the contracted annulus to snap forward again, thus dislodging and launching the spores away from the plant. The type and position of the annulus is variable (e.g. patch, apical, oblique, or vertical) and can be used to distinguish major groups of leptosporangiate ferns.
Fern spikes cannot occur without ferns already existing in the area, so spikes occur primarily in regions where ferns are already a prominent part of the ecosystem. At the Cretaceous-Paleogene extinction event, a fern spike occurred in the New Zealand area, where ferns made up 25% of plant abundance pre-extinction.
Plants often grow in dense clumps in mud along the shores of ponds or streams, or they may grow submerged in shallow water with some of the leaves extending to float on the water surface. They grow in seasonally wet habitats, but survive the winter or dry season by losing their leaves and producing hard, desiccation-resistant reproductive ...
Azolla (common called mosquito fern, water fern, and fairy moss) is a genus of seven species of aquatic ferns in the family Salviniaceae. They are extremely reduced in form and specialized, looking nothing like other typical ferns but more resembling the form of some mosses or even duckweeds .
A plant will abscise a part either to discard a member that is no longer necessary, such as a leaf during autumn, or a flower following fertilisation, or for the purposes of reproduction. Most deciduous plants drop their leaves by abscission before winter, whereas evergreen plants continuously abscise their leaves. Another form of abscission is ...
For the spores to be able to start growing, it must fall into wet ground. A spore that falls into dry land, will never begin to grow, since it needs to absorb water. Once the spore has settled down it can start absorbing water through osmosis, which enables swelling and bursting of the outer walls of the spore and the growing tissue can be ...
The term "fern ally" included under Pteridophyta generally refers to vascular spore-bearing plants that are not ferns, including lycopods, horsetails, whisk ferns and water ferns (Marsileaceae, Salviniaceae and Ceratopteris). This is not a natural grouping but rather a convenient term for non-fern, and is also discouraged, as is eusporangiate ...
Pressed closely but not fused, e.g. leaves against a stem. aquatic plant A plant whose natural habitat is water, living in or on water for all or a substantial part of its lifespan; generally restricted to fresh or inland waters. arachnoid Cobwebby, from being covered with fine white hairs. arborescent Tree-like in growth or general appearance ...