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All vascular plants are sporophyte dominant, and a trend toward smaller and more sporophyte-dependent female gametophytes is evident as land plants evolved reproduction by seeds. [7] Those vascular plants, such as clubmosses and many ferns, that produce only one type of spore are said to be homosporous.
Heterospory evolved due to natural selection that favoured an increase in propagule size compared with the smaller spores of homosporous plants. [ 2 ] Heterosporous plants, similar to anisosporic plants [ clarification needed ] , produce two different sized spores in separate sporangia that develop into separate male and female gametophytes.
Equisetum (/ ˌ ɛ k w ɪ ˈ s iː t əm /; horsetail) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. [2]Equisetum is a "living fossil", the only living genus of the entire subclass Equisetidae, which for over 100 million years was much more diverse and dominated the understorey of late Paleozoic forests.
Equisetidae is one of the four subclasses of Polypodiopsida (ferns), a group of vascular plants with a fossil record going back to the Devonian. They are commonly known as horsetails . [ 2 ] They typically grow in wet areas, with whorls of needle-like branches radiating at regular intervals from a single vertical stem.
A pteridophyte is a vascular plant (with xylem and phloem) that reproduces by means of spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as "cryptogams", meaning that their means of reproduction is hidden. They are also the ancestors of the plants we see today.
Most non-vascular plants, as well as many lycophytes and most ferns, are homosporous (only one kind of spore is produced). Some lycophytes, such as the Selaginellaceae and Isoetaceae , [ 7 ] : 7 the extinct Lepidodendrales , [ 8 ] and ferns, such as the Marsileaceae and Salviniaceae are heterosporous (two kinds of spores are produced).
The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers.They differ from mosses by being vascular, i.e., having specialized tissues that conduct water and nutrients, and in having life cycles in which the branched sporophyte is the dominant phase.
Plants that are homosporous produce spores of the same size and type. 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".