Septalaria, also known as Paleozoic (primitive) Perianthia, isAngiospermaDicotyledons(also called Magnolia)SubclassThey include the type of flowers with no quilt, single flower or calyx and corolla, and the petals are usually separated.Stamens and corolla free.ovuleThere is usually a bead quilt.[1-2]
The subclass of Septaloba is also called Archahymydeae.includeQuiltless flower，Monogamous flowerOr have calyx and corolla difference, and petal usually separate type.Stamens and corolla free.The ovule generally has a integument.
This subclass is also called Metachlamydeae, and its main feature is how many petals are unitedValvate corolla。Corolla forms various shapes, such as funnel, bell, lip, tube, tongue, etc., from radial symmetry to bilateral symmetry.The various combinations of corolla increase the adaptability to insect pollination and the protection of stamens and pistils.Therefore, the synpetal flower group is more evolved than the detached flower group.
Platycodon grandiflorum flower[1]
The number of flower cycles tends to decrease from 5 cycles (1 cycle of calyx, 1 cycle of petal, 2 cycles of stamen, 1 cycle of carpel of pistil, such as azalea, persimmon family, etc.) to 4 cycles (1 cycle of calyx, petal, stamen, carpel, such as oleaceae, honeysuckle family, etc.), and the number of each cycle also gradually decreases, such as the number of stamens from the same number as the corolla lobes, such as 5 (Convolvulaceae, Solanaceae, Primulaceae, etc.)It is reduced to 4-2 (Labiatae, Cucurbitaceae), and the number of carpels is reduced from 5 (Rhododendron) to 2 (most of the carpels of the four wheeled flowers are 2).
Usually without stipules, the ovule has only one layer of perisperm.
Since the 19th century, many plant taxonomists have made great efforts to establish a "natural" classification system.According to their phylogenetic theories, they have proposed dozens of classification systems.However, due to the lack of knowledge about the origin and evolution of angiosperms, especially fossil evidence, there is no relatively complete classification system until now.At present, Engler system andHutchinson system。In the arrangement of classification systems at all levels, the Kronquist system and the Taheta system are considered more reasonable.
This is the system used by the German taxonomists A. Engler and K. PrantI in their great book "The Natural Branch of Plants" in 1897. It is the first relatively complete system in the history of taxonomy. It divides plants into 13 phyla, and the 13th phyla isSpermatophyta, divided into gymnosperms and angiosperms,AngiospermaIt includes monocotyledons and dicotyledons, andDicotyledonsIt is divided into the subclass of detached flowers (Paleoperianth) and the subclass of sympetalous flowers (Metaperianth).
Engler's system put monocotyledons before dicotyledons, and put the plants of sympetalous flowers into one group. It considered them to be an evolutionary group of plants. It regarded catkin plants as the most primitive group of dicotyledons, and Magnolia, Ranunculaceae, etc. as relatively evolutionary groups. Many modern taxonomists do not agree with these views.
The Sigler system has been revised several times. In the twelfth edition of the Records of Plant Subdivisions published in 1964, dicotyledons were placed before monocotyledons.There are 62 orders and 344 families, including 48 orders and 290 families of dicotyledons and 14 orders and 54 families of monocotyledons.Textbook of medicinal botanyThe revised Sigler system is adopted for the classification of angiosperms, but some contents are changed.
This is the system established by the British botanist J. Hutchinson in his Flora I and II in 1926 and 1934.In the third edition revised in 1973, there were 111 orders, 411 families, including 82 orders, 342 families of dicotyledons and 29 orders, 69 families of monocotyledons.
Hutchinson systemIt is believed that the multicarped Magnoliales and Ranunculaceae are the original groups of angiosperms, but the two sources of woody and herbaceous plants are overemphasized. It is believed that woody plants are evolved from Magnoliales and herbaceous plants are evolved from Ranunculaceae. As a result, some families closely related are far apart in the systematic position, such as the umbelliferae of herbaceous plants and the cornaceae and acanthopanaceae of woody plants;This view is also opposed by most modern taxonomists.
This is the system published by A. Takhtajan, a botanist of the former Soviet Union, in his book Origin of Angiosperms in 1954. He first broke the traditional classification of dicotyledons into the subclass of detached flowers and the subclass of sympetalous flowers;The first level classification unit of "super order" is added to the classification level.He made Paeonia, formerly belonging to Ranunculaceae, independent into Paeoniaceae, etcCytotaxonomyandChemotaxonomyThe development coincides with that of the international consensus.
Takhtajan system After many revisions, in the 1980 revision, there were 28 superorders, 92 orders, 416 families, including 20 superorders, 71 orders, 333 families, and 8 superorders, 21 orders, 77 families of monocotyledonous plants (Liliaceae).
This is the system published by American botanist A. Cronquist in his book Classification and Evolution of Floral Plants in 1968.In the 1981 revision, there were 83 orders and 388 families, including 64 orders and 318 families of dicotyledons and 19 orders and 65 families of monocotyledons.
Kronquist system is close toTakhtajan system ，把Angiosperma(called Magnolia Phyta) is divided into Magnolia and Liliacea, but the first class taxon of "super order" has been canceled, and the division of families is also less than that of the Taheta system.At present, textbooks in China use this system.
The two schools of systematic evolution have long been the center of plant taxonomists' research and the focus of controversy on the morphological characteristics of the oldest angiosperms and the respective morphological characteristics of primitive and evolutionary groups. In particular, there are the greatest differences of opinion on the origin of the "flowers" of angiosperms, forming two schools, the so-called "pseudo flower school"And "Zhenhua School", or "Rucatu School" and "Ranunculus School".The former is represented by German botanist Engler, while the latter is represented by American botanists Bosch and Khalil, and British botanist Hutchinson.
1、 False flower school
It is believed that angiosperm flowers and gymnosperm bulbs are identical, and each stamen and carpel is equivalent to one extremely degenerated male flower and female flower respectively, so it is assumed that angiosperm is from gymnospermEphedra officinalisIn this scenario, the bracts of male flowers become perianths, and the bracts of female flowers become carpels. After the bracteoles of each male flower disappear, only one stamen remains, and after the bracteoles of female flowers disappear, only ovules remain, which are born at the base of the ovary.Since gymnosperms, especially Ephedra and Mahogany, are dominated by unisexual flowers, it is assumed that primitive angiosperms have unisexual flowers.This theory is calledPseudanthium theory (Pseudanthium theory)。According to this, the primitive group of modern angiosperms should have unisexual flowers, angiosperms, wind pollinated flowers and woody soft Yi inflorescence plants, such asCasuarina, pepper, willow, etc.The viewpoint of this school is opposed by most modern systematicians. According to anatomical, palynological and other research data, catkin should be a secondary group.
