In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, fungi and protozoa.
A sporangium ; pl.: sporangia) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cycle. Sporangia can produce spores by mitosis, but in nearly all land plants and many fungi, sporangia are the site of meiosis and produce genetically distinct haploid spores.
Isoetes, commonly known as the quillworts, is a genus of lycopod. It is the only living genus in the family Isoetaceae and order Isoetales. There are currently 192 recognized species, with a cosmopolitan distribution mostly in aquatic habitats but with the individual species often scarce to rare. Some botanists split the genus, separating two South American species into the genus Stylites, although molecular data place these species among other species of Isoetes, so that Stylites does not warrant taxonomic recognition. Species virtually identical to modern quillworts have existed since the Jurassic epoch, though the timing of the origin of modern Isoetes is subject to considerable uncertainty.
Isoetes lacustris, the lake quillwort or Merlin's grass, is a boreal quillwort native on both sides of the northern Atlantic Ocean. Synonyms include Isoetes hieroglyphica.
Isoetales, sometimes also written Isoëtales, is an order of plants in the class Lycopodiopsida.
Isoetes bolanderi, or Bolander's quillwort, is a species of quillwort, a type of lycophyte. This aquatic plant is native to high altitude regions of the western United States and southern Alberta. It grows almost entirely underwater in lakes and other water bodies from a corm-like stem, which remains buried in the mud, producing up to twenty pointed, cylindrical leaves approaching 15 centimeters in maximum length. It reproduces via spherical sporangia, covered about one third by the velum. The ligule is small and heart-shaped. The megaspores are white, though sometimes bluish, and 350 to 290 micrometers in diameter. The microspores are 25 to 30 micrometers long.
Isoetes howellii, or Howell's quillwort, is a species of quillwort, a type of lycophyte. It is an aquatic plant native to North America.
Isoetes nuttallii, or Nuttall's quillwort, is a species of quillwort, a type of lycopod. It is native to shallow waters and other wet habitats of western North America from British Columbia to California. It produces up to 60 pointed, cylindrical, green to gray-green leaves, each 7 to 17 centimeters long. The velum completely covers the spherical sporangia, which are 5 millimeters long and 1.5 millimeters wide. The ligule is small and triangular. The megaspores are 400 to 500 micrometers in diameter. The microspores, which are spiny and covered in tubercles, are 28 to 31 micrometers long.
Isoetes echinospora, also known as spiny quillwort, spiny-spored quillwort or spring quillwort is a species of quillwort in the Isoetaceae family, and is the most abundant species in Canada. It can be found in shallow aquatic environments from Labrador and Newfoundland to Alaska, and south to Pennsylvania, Wisconsin, Michigan, Colorado, and California. In Germany it is found in only two locations: the Feldsee and Lake Titisee, both in the High Black Forest.
Isoetes × eatonii, or Eaton's quillwort, is a hybrid between I. engelmannii and I. tenella. It can be found in ponds and slow moving rivers in Canada or in several New England states. In Canada, it has only been found in the Severn River in Ontario. In the United States, it has been found in Pennsylvania, New Jersey, and New York. It bears 12-100 long yellowish green leaves, each fine, soft, and 8 to 45 centimeters long. The unspotted tan colored sporangium are 12 millimeters long and 5 millimeters wide. The velum covers a sixth to a quarter of the sporangium. The elongated ligule is 3.5 millimeters long. The flattened white megaspores are 320 to 530 micrometers in diameter and bear short spiny ridges. The round microspores are 22 to 25 micrometers long.
Isoetes riparia, the shore quillwort, is a species of plant in the family Isoetaceae. It can be found in rivers, creeks, and tidal mud flats in southern Quebec and southeastern Ontario, south to eastern New York. It has 5 to 35 long, erect bright green to yellow-green leaves, which are 6 to 35 centimeters long. The velum covers one fourth of the sporangium, which can be 7 millimeters long and 4 millimeters wide. The elongated ligule can grow to be 3 millimeters long. The spherical megaspores are 430 to 680 micrometers in diameter with closely set ridges. The kidney-shaped microspores are 24-35 micrometers long, and usually have spine-tipped tubercules. The megaspores can sometimes come to resemble that of either I. echinospora, if the megaspores become eroded and bear projections that could resemble spines, or I. macrospora, if the broken ridges take a certain shape.
Isoetes acadiensis, the Acadian quillwort is a species of quillwort in the Isoetaceae family described by Kott in 1981. It can be found along the shores of lakes, ponds, and rivers in Newfoundland, Nova Scotia, and New Brunswick, as well as in the American states Maine, Massachusetts, and New Hampshire. It has a similar distribution to that of I. tuckermanii. It bears 9 to 35 mostly recurved leaves, each 5–21 cm long. The leaves are usually dark green, though can occasionally be tinged with red. The sporangium can be up to five millimeters long and 3 millimeters in length, covered one sixth to one third by the velum. The spherical megaspores are 400-570 micrometers in diameter, and bear smooth ridges. The kidney shaped microspores are 25 to 30 micrometers long. It was originally believed to be a member of Isoetes hieroglyphica because of their similar megaspore structure.
Isoetes macrospora, the big-spore quillwort, is a species of quillwort in the Isoetaceae family. It can be found in the deep water of low nutrient lakes in the Precambrian Shield as well as in Newfoundland, Nova Scotia, Quebec, and Ontario. In the United States, it has been found in Minnesota and south, through the Appalachian Mountains to Virginia. It bears 3 to 17 long, stiff dark green leaves, sometimes with recurving tips. The sporangium can be 5 millimeters long and 4 millimeters wide, covered from one sixth to one quarter by the velum. The triangular ligule can grow up to 2 millimeters long. The spherical, white megaspores are 400 to 800 micrometers in diameter, and bear ridges that form honeycomb-like areas. The kidney-shaped microspores are 32 to 50 micrometers long, each with evenly spaced smooth papillae.
Isoetes tuckermanii, or Tuckerman's quillwort, is a tetraploid species of plant in the family Isoetaceae. It can be found in shallow water in Newfoundland, Nova Scotia, New Brunswick, and south through the New England states to Maryland. It bears 10 to 45 long bright green to yellow green leaves that are 4 to 25 centimeters long, usually erect, but sometimes recurved. The velum covers one fourth or less of the sporangium, which is usually unspotted, 5 millimeters long, and 3 millimeters wide. The white spherical megaspores are 400 to 650 micrometers in diameter, and bear rough-crested ridges that form a hexagonal honeycomb shape. The kidney shaped microspores are 24 to 33 micrometers long, bearing tubercles. It is very similar to I. macrospora, only reliably distinguishable by cytology or through careful megaspore measurement.
Isoetes occidentalis, the western quillwort, is a species of quillwort in the family Isoetaceae. It can be found in aquatic habitats of coastal Alaska and British Columbia south to California and Colorado. It is frequently found on Vancouver Island and around the Fraser Valley region. It bears 10 to 30 or more rigid, dark green leaves, each 5 to 20 centimeters long. The velum covers one fourth to one third of the orbicular sporangium, which is 5 to 6 millimeters in diameter. The ligule is shaped like a shortened triangle. The white megaspores are 500 to 700 micrometers in diameter and bear sharp ridges and crests. The microspores are 36 to 43 micrometers long. Though the leaves seem to bear resemblance to those of I. lacustris, especially the occasionally occurring reddish base, I. occidentalis is a hexaploid and I. lacustris is a decaploid.
Isoetes brevicula is a quillwort species native to Western Australia. It is a cormous, perennial, herb or, to 1 cm (0.39 in) high, stock 3-lobed; leaves 4–8 mm (0.16–0.31 in) long; mature megaspores greyish white when dry. Submerged in rock pools on granitic outcrops.
Isoetes capensis, the cape quillwort, is a species of quillwort from South Africa.
Isoetes stellenbossiensis, the Stellenbosch quillwort or Cape Flats quillwort, is a species of plant from South Africa.
Isoetes stephanseniae, the granite quillwort, is a species of quillwort from South Africa, named for A. J. Stephansen, who discovered it in 1927. Of very limited distribution, it is known to survive only as one population in seasonal pools over granite near Stellenbosch, where it is threatened by the encroachment of alien species and eutrophication from the sewage works on whose grounds it grows. Like other quillworts, it bears a tuft of leaves with distinctively sculpted megaspores. It is most similar to Isoetes capensis, the cape quillwort, which occurs in the same province; both hold their leaves at a 45-degree angle, unlike most South African quillworts which have leaves stiffly erect.
