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Vascular Plants Without Seeds (Origin of Megaphylls (Euphylls) (megaphylls…
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- diplontic life cycle — the diploid stage is multicellular and haploid gametes are formed, meiosis is "gametic". haplodiplontic life cycle (also referred to as diplohaplontic, diplobiontic, or dibiontic life cycle) — multicellular diploid and haploid stages occur, meiosis is "sporic".
- having only one multicellular generation
- A hypothetical account for the emergence of a sporophyte generation during the evolution of vascular plants. It postulates that early plants were exclusively haploid gametophytes. At some point a zygote ‘germinated’ mitotically instead of meiotically, producing a rudimentary diploid sporophyte. Hence, a sporophyte generation was ‘inserted’, or interpolated, into the life cycle. The sporophyte evolved to become increasingly elaborate and the more prominent form – as in modern seed plants – while the gametophyte became progressively reduced.
- In dichotomous branching, two branches of equal thickness are formed at every point of branching.
- Rhyniophytina is a subdivision of extinct early vascular plants that are considered to be similar to the genus Rhynia, found in the Early Devonian. Sources vary in the name and rank used for this group, some treating it as the class Rhyniopsida, others as the division Rhyniophyta.
- a simple, primitive arrangement of conducting tissues in stems and roots of certain lower plants, consisting of a solid cylinder of xylem surrounded by a layer of phloem. Origin of protostele.
- are a defining characteristic of the lycophyte lineage.
- a stele consisting of a core of pith surrounded by concentric layers of xylem and phloem.
- The spermatophytes, also known as phanerogams or phaenogams, comprise those plants that produce seeds, hence the alternative name seed plants. They are a subset of the embryophytes or land plants.
- A group of extinct vascular plants that lived in the Devonian period. They were small herbs, similar in many ways to the rhyniophytes; for example, members of the principal genus, Zosterophyllum, grew about 15 cm tall in swampy areas and had naked stems that branched dichotomously (equally). However, other members evolved lateral branches and scalelike outgrowths. Moreover, the arrangement of their spore-forming organs and xylem indicates that they represent a line of evolution, separate from the rhyniophytes, that led to the lycophytes (e.g. clubmosses) but not to the seed plants.
- Enations are scaly leaflike structures, differing from leaves in their lack of vascular tissue. They are created by some leaf diseases. Also found on some early plants such as Rhynia, where they are hypothesized to aid in photosynthesis.
- In plant anatomy and evolution a microphyll is a type of plant leaf with one single, unbranched leaf vein. Plants with microphyll leaves occur early in the fossil record, and few such plants exist today. In the classical concept of a microphyll, the leaf vein emerges from the protostele without leaving a leaf gap.
- A strobilus (plural: strobili) is a structure present on many land plant species consisting of sporangia-bearing structures densely aggregated along a stem.
- A ligule —is a thin outgrowth at the junction of leaf and leafstalk of many grasses and sedges. A ligule is also a strap-shaped extension of the corolla, such as that of a ray floret in plants in the daisy family Asteraceae.
- or pseudomonopodial growth is a growth habit in which branches depart from a main (usually vertical) axis, rather than by more or less even bifurcation of the axis. To put the matter more simply, overtopping means branching more like a tree and less like a bush.
- A type of branching where the apical meristem appears to divide to form two branches, one of which is dominant resulting in an upright main axis with distinct side branches. Pyrenoid: An area of starch formation found in the chloroplasts of certain algae.
- A leaf with several or many large veins branching apart or running parallel and connected by a network of smaller veins. The fronds of ferns and the leaves of gymnosperms and angiosperms are megaphylls. Megaphylls are thought to have evolved from groups of branched stems that have become fused together.
- The theory that the leaves (megaphylls) of ferns and seed plants evolved by the modification of terminal branches (telomes) of stems. It envisages that firstly, instead of the primitive equal (dichotomous) branching of the stem, there developed a main axis with lateral side branches.
- In the telome theory of the origin of megaphylls, the concept that the lamina originated by the production of parenchyma cells between the telomes.
- A sporophyll is a leaf that bears sporangia. Both microphylls and megaphylls can be sporophylls. 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 euphyllophytes are a clade of plants within the tracheophytes. The group may be treated as an unranked clade, a division under the name Euphyllophyta or a subdivision under the name Euphyllophytina.
- The term “pteridophyte” has fallen out of favor since it is not one monophyletic grouping like the monilophytes (Schuettpelz, 2004). The main organism that we see, the growing and the adult fern, known as a sporophyte, is diploid. Diploidy in organisms means that they have two sets of chromosomes.
- The euphyllophytes are a clade of plants within the tracheophytes. The group may be treated as an unranked clade, a division under the name Euphyllophyta or a subdivision under the name Euphyllophytina.
- Lignophytes are a clade of vascular plants that consists of seed plants and progymnosperms (a paraphyletic assemblage from which the seed plants arose). It is thought that by the transition from free-sporing heterospory to gymnospermous reproduction that the gymnosperms were derived from the progymnosperms.
- a horsetail with a very rough ridged stem, formerly used for scouring and polishing.
- A receptacle in ferns which bears the sporangia, usually a stalk, but sometimes a scale (as in horsetails). (mycology) A special type of hypha that bears sporangia on the tip.
- Vascular plants with monopodial growth habits grow upward from a single point. They add leaves to the apex each year and the stem grows longer accordingly. The word Monopodial is derived from Greek "mono-", one and "podial", "foot", in reference to the fact that monopodial plants have a single trunk or stem.
- Polypodiidae, commonly called leptosporangiate ferns, is a subclass of ferns. It is the largest group of living ferns, including some 11000 species worldwide. They constitute the subclass Polypodiidae, but are often considered to be the class Pteridopsida or Polypodiopsida, although other classifications assign them a different rank.The leptosporangiate ferns are one of the four major groups of ferns, with the other three being the Eusporangiate ferns comprising the marattioid ferns (Marattiidae, Marattiaceae), the horsetails (Equisetiidae, Equisetaceae), and whisk ferns and moonworts.
- a strand of conducting vessels extending from the stem to the base of a leaf.
- A leaf gap is a space in the stem of a plant through which the leaf grows. The leaf is connected to the stem by the leaf trace, which grows through the leaf gap. The leaf gap is a break in the vascular tissue of a stem above the point of attachment of a leaf trace.
- are created for types of isolated organs, tissues, spores, or pollen.
- sori) is a cluster of sporangia (structures producing and containing spores) in ferns and fungi. This New Latin word is from Ancient Greek σωρός (sōrós 'stack, pile, heap'). In lichens and other fungi, the sorus is surrounded by an external layer.
- a sporangium that arises from a group of epidermal cells. sporangium, spore case, spore sac - organ containing or producing spores.
- A sporangium formed from a single epidermal cell.
- Vascular Cryptogam is an old botanical phrase, and it refers to those vascular plants that do not make seeds. Thus, cryptogam (literally hidden gametophyte) refers to the production of a separate, usually very small, archegoniate gametophyte. These are well represented in the fossil record.
- Fern allies are a diverse group of seedless vascular plants that are not true ferns. Like ferns, a fern ally disperses by shedding spores to initiate an alternation of generations.
