Gnetopsida refers toGymnospermaAn outline of.There are about 80 species belonging to 3 genera, 3 families, 3 orders and 3 families in the class Gnetaceae.There are 19 species in 2 orders, 2 families, 2 genera in China.shrubOr woody vines, sparse trees or herbaceous shrubs.Mosaicans are generallyshrub, arbor orLianaThe common ones are Mai Ma Teng (Ni Teng), Xiao Ye Mai Ma Teng (Xiao Sample Mai Ma Teng, Gou Nu Teng).
Shrubs or woody vines, rare trees or herbaceous shrubs.Secondary xylemThere is usually a duct without resin duct.The leaves are opposite or whorled, and there are various types of leaves;There are small membranous sheaths or green flat dicotyledonous plants.The cones are unisexual, heteroecious or homoecious, or have bisexual marks, and have a perianth like covering, also called pseudoperianth, which is membranous, leathery or fleshy;1 ovule, 1-2 layers of integument, with micropylar tube;Sperm has no cilia;The archegonium is extremely degenerated or absent;Mature female cones are in the shape of cones, berries or slender spikes.The seeds are enclosed in the aril developed from the operculum, with 1-2 layers of seed coat, abundant endosperm and 2 cotyledons.
There are 3 orders, 3 families, 3 genera and about 80 species of plants in the class Gneiss.There are 19 species in 2 orders, 2 families, 2 genera in China, which have been distributed over the country for several times.This kind of plants originated in the Cenozoic era.IntrastematicSecondary xylemThere are vessels, sporophylls have a mantle, ovules are wrapped in the mantle, and many species have multinucleate embryo sacs without neck and socket organs. These characteristics are the characteristics of the most evolved group of gymnosperms[1]。
morphological character
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The secondary xylem in the stems of this class of plants has vessels, no resin ducts, the sporophyll has a mantle, and the ovule is wrapped in the mantle. Many species have multinucleate embryo sacs without neck snow organs. These characteristics are the characteristics of the most evolved group in gymnosperms.The leaves are opposite or whorled. There are various types of leaves, which are small membranous sheaths, or green flat like dicotyledons, or fleshy and extremely long, like monocotyledons in strips.The sporophyll is unisexual, heteroecious or homoecious, or has bisexual traces, and has a cover similar to the perianth, which is called "pseudoperianth". The cover is membranous, leathery or fleshy;Ovule 1, integument 1~2 layers, micropylar tube;Sperm has no cilia;The archegonium is extremely degenerated or absent;matureMegasporiumThe ball is cone shaped, berry shaped or slender spike shaped.The seeds are wrapped in the aril developed from the mantle, with 1-2 layers of seed coat and abundant endosperm[2]。
It is distributed in the south subtropical and middle subtropical regions, with the southern part of the Asian continent, from Malay Islands to the Philippines as its distribution center.It is distributed in southeast and southwest China.
Ephedraceae
It is distributed in the arid desert and grassland areas of Asia, America, southeast Europe and northern Africa.In addition to the provinces and autonomous regions in the lower reaches of the Yangtze River and the Pearl River basin, other provinces and autonomous regions are distributed in China, with more species in the northwest, Yunnan, Sichuan, Tibet and other provinces and autonomous regions.
Centenarian Lanke
It is distributed in the desert area near the coast in southwest Africa.
Growth environment
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Maceraceae
Born in tropical rainforests and monsoon forests, it can surpass the Tropic of Cancer in southern Asia and reach the central subtropical region, climbing the trunk and branches of trees and trees.They prefer hot and humid climate or warm and humid habitat in dry and wet seasons.
Ephedraceae
Most of them are xerophytic or semi xerophytic plants, which are found in sand dunes, semi deserts, grasslands, deserts and sparsely forested arid areas.
Centenarian Lanke
It is a typical xerophyte in the desert area near the coast.
classification method
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Echinacea
According to the traditional classification method, the class Gnathophyllum is included inGymnosperma, but cannabinoidBotanyMore than othersGymnospermsMore evolved,XylemWith vessel, no resin, large leaves, similar to monocotyledon, and similar to sporophyllperianthThe latest classification method lists them as oneBuying Mateng Gate。
Subordinate classification
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Maceraceae
Most of them are winding, climbing or ascending woody vines, and few are upright trees or shrubs;The stem and branch have nodes, and the nodes are connected by the upper and lower parts, expanding into a joint shape. The lower top edge has a ring of involucral bracts. The primary xylem is composed of tracheids, and the secondary xylem has vessels.Single leaf opposite, petiolate, without stipules, leathery leaves, with feather veins and net veins, very similar to the leaves of dicotyledons.Floral unisexuality,Dioecious, sparsely monoecious, the bulbs elongate into slender spikes, with multiple rings of synthetic annular involucral bracts;The false perianth of the female flower is saccate and tightly encloses the ovule. The inner ovule of the ovule is extended into a perianth tube at the top and extends out of the false perianth. The outer perianth develops into a fleshy outer layer and a bone inner layer, and the fleshy outer layer and the false perianth combine to form a false seed coat.The seed is drupe shaped, the aril is red or orange when it is mature, the endosperm is rich and fleshy.There is only one genus and about 30 species.
Ephedraceae
They are multi branched shrubs, subshrubs or herbaceous, and the plants are usually short, with upright or creeping stems and vessels in the secondary xylem;Branchlets opposite or whorled, green, with nodes, and several thin longitudinal grooves between nodes.The leaves degenerate into membranous, 2-3 opposite or whorled on the nodes, about 1/2 or 2/3 united into a sheath, and the upper part is triangular teeth.It is dioecious, sparsely monoecious, with ovoid or elliptic cones, shoot tops or leaf axils, and 2-8 pairs of alternate opposite or whorled membranous bracts.Only one genus, about 40 species, is distributed in all provinces and autonomous regions except the provinces and autonomous regions in the lower reaches of the Yangtze River and the Pearl River basin. There are more species in the northwest, Yunnan, Sichuan, Tibet and other provinces and autonomous regions, while the resources are rich in the northern provinces and autonomous regions.Ephedra has the function of fixing sand and protecting soil.
Centenarian Lanke
There is only one genus and one species, namely Welwitschia mirabilis.The plant has a unique shape, which is different from other gymnosperms.The stem is short and thick, blocky, with conical roots deep into the ground.In addition to one pair of cotyledons in the seedling stage (falling off after 2-3 years), the plant has only one pair of large zonal cotyledons in its lifetime, which are 2-3 meters long and about 30 cm wide, and can survive for more than 100 years, hence the name.The sporophyll spheroid is unisexual, born in the depression of stem top;The bracts of bulbous sporophyll are alternately opposite, arranged neatly and bright red.The microsporophyll ball has six basal connate microsporophylls, and one incompletely developed ovule in the center.MegasporiumThe integument is tubular, the ovule has a layer of integument, and the top of the integument extends into a micropylar tube.The fertilization of the archegonia is carried out by the encounter between the tubular protuberances growing upward from the top of the female gametophyte and the pollen tubes growing downward from the nucellus.
