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Modern heterosporous plants such as many ferns exhibit endospory, in which a megagametophyte is fertilized by a microgametophyte all while still inside the spore wall, gaining nutrients from the inside of spore. [6] Both heterospory and endospory seem to be one of the many precursors to seed plants and the ovary.
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 ...
Salviniales are all aquatic and differ from all other ferns in being heterosporous, meaning that they produce two different types of spore (megaspores and microspores) that develop into two different types of gametophyte (female and male gametophytes, respectively), and in that their gametophytes are endosporic, meaning that they never grow outside the spore wall and cannot become larger than ...
In heterosporous plants, sporophylls (whether they are microphylls or megaphylls) bear either megasporangia and thus are called megasporophylls, or microsporangia and are called microsporophylls. The overlap of the prefixes and roots makes these terms a particularly confusing subset of botanical nomenclature.
Heterosporous plants, such as seed plants, spikemosses, quillworts, and ferns of the order Salviniales produce spores of two different sizes: the larger spore (megaspore) in effect functioning as a "female" spore and the smaller (microspore) functioning as a "male".
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.
As heterosporous plants, fertile Isoetes sporophytes produce megaspores and microspores, which develop in the megasporangia and microsporangia. [17] These spores are highly ornate and are the primary way by which species are identified, although no one functional purpose of the intricate surface patterns is agreed upon. [ 18 ]
Salviniaceae (/ s æ l ˌ v ɪ n i ˈ eɪ s i ˌ iː /), [1] [2] is a family of heterosporous ferns in the order Salviniales. [3] The Salviniaceae contain the two genera Azolla and Salvinia, [4] with about 20 known species in total. [5] The oldest records of the family date to the Late Cretaceous. [6]