Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching stems bearing simple leaves called microphylls and reproduce by means of spores borne in sporangia on the sides of the stems at the bases of the leaves. Although living species are small, during the Carboniferous, extinct tree-like forms (Lepidodendrales) formed huge forests that dominated the landscape and contributed to coal deposits.
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.
A pteridophyte is a vascular plant that disperses spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as "cryptogams", meaning that their means of reproduction is hidden.
Isoetales, sometimes also written Isoëtales, is an order of plants in the class Lycopodiopsida.
Microspores are land plant spores that develop into male gametophytes, whereas megaspores develop into female gametophytes. The male gametophyte gives rise to sperm cells, which are used for fertilization of an egg cell to form a zygote. Megaspores are structures that are part of the alternation of generations in many seedless vascular cryptogams, all gymnosperms and all angiosperms. Plants with heterosporous life cycles using microspores and megaspores arose independently in several plant groups during the Devonian period. Microspores are haploid, and are produced from diploid microsporocytes by meiosis.
Isoetes valida, commonly known as the strong quillwort or true quillwort, is an aquatic lycophyte native to eastern North America. It is found primarily in the Appalachian Mountains from Pennsylvania south to Alabama and Georgia. In addition, one collection of the plant was made in a railway ditch in Wilmington, Delaware in the 1860s, but this was most likely an accidental introduction.
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.
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.
Isoetes maritima, the maritime quillwort, is a quillwort in the Isoetaceae family. It is native to Alaska, British Columbia, and Washington state. It bears eight to fifteen dark green, erect, rigid leaves that are each two to five centimeters long and 1.5 millimeters wide. The oval sporangia are small and inconspicuous, measuring at four millimeters long. The velum covers a third to a half of the sporangia. The white microspores are kidney-shaped and 30-36 micrometers long. The white megaspores are spherical and 490-670 micrometers in diameter. It is similar to I. echinospora, but with blunt spines and crests on the megaspores. I. echinospora has sharp, thin spines, though most of the other species in the genus have no megasporal spines. The epithet "maritima" and the common name "maritime quillwort", meaning "of the sea or ocean", are misnomers. Because it was first discovered by Macoun near tidal flats in British Columbia, it was treated as a coastal species. Since that time, however, it has been found in fresh-water lakes and streams.
Isoetes caroliniana, common name Carolina quillwort, is a wetlands plant native to the mountains of Tennessee, North Carolina, Virginia and West Virginia. It is an emergent plant found in lakes and bogs. It is closely related to I. georgiana but can be distinguished by its unpigmented sporangium wall.
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 butleri, commonly known as limestone quillwort, is a species of plant in the quillwort family, a member of the lycophytes.
