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A catkin or ament is a slim, cylindrical flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

 cluster, with inconspicuous or no petal
Petals are modified leaves that surround the reproductive parts of flowers. They often are brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals lying...

s, usually wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...

Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Anemophilous plants may be either gymnosperms or angiosperms ....

) but sometimes insect pollinated (as in Salix). They contain many, usually unisexual
Plant sexuality
Plant sexuality covers the wide variety of sexual reproduction systems found across the plant kingdom. This article describes morphological aspects of sexual reproduction of plants....

 flowers, arranged closely along a central stem which is often drooping. They are found in many plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

 families, including Betulaceae
Betulaceae, or the Birch Family, includes six genera of deciduous nut-bearing trees and shrubs, including the birches, alders, hazels, hornbeams and hop-hornbeams, numbering about 130 species...

, Fagaceae
The family Fagaceae, or beech family, comprises about 900 species of both evergreen and deciduous trees and shrubs, which are characterized by alternate simple leaves with pinnate venation, unisexual flowers in the form of catkins, and fruit in the form of cup-like nuts. Fagaceous leaves are often...

, Moraceae
Moraceae — often called the mulberry family or fig family — are a family of flowering plants comprising about 40 genera and over 1000 species. Most are widespread in tropical and subtropical regions, less so in temperate climates...

, and Salicaceae
Salicaceae are a family of flowering plants. Recent genetic studies summarized by the Angiosperm Phylogeny Group has greatly expanded the circumscription of the family to contain 55 genera....

. For some time, they were believed to be a key synapomorphy
In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...

 among the proposed Hamamelididae
Hamamelididae is a botanical name at the rank of subclass. A well-known system that used this name is the Cronquist system, although in the disallowed spelling Hamamelidae...

, but it is now believed that this flower arrangement has arisen independently by convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...

 on a number of occasions.

In many of these plants only the male flowers form catkins, and the female flowers are single (hazel
The hazels are a genus of deciduous trees and large shrubs native to the temperate northern hemisphere. The genus is usually placed in the birch family Betulaceae, though some botanists split the hazels into a separate family Corylaceae.They have simple, rounded leaves with double-serrate margins...

, oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...

), a cone (alder
Alder is the common name of a genus of flowering plants belonging to the birch family . The genus comprises about 30 species of monoecious trees and shrubs, few reaching large size, distributed throughout the North Temperate Zone and in the Americas along the Andes southwards to...

) or other types (mulberry
Morus is a genus of flowering plants in the family Moraceae. The 10–16 species of deciduous trees it contains are commonly known as Mulberries....

). In other plants (such as poplar
Populus is a genus of 25–35 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar , aspen, and cottonwood....

) both male and female flowers are borne in catkins.

Catkin-bearing plants include many other trees or shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...

s such as birch
Birch is a tree or shrub of the genus Betula , in the family Betulaceae, closely related to the beech/oak family, Fagaceae. The Betula genus contains 30–60 known taxa...

, willow
Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...

, hickory
Trees in the genus Carya are commonly known as hickory, derived from the Powhatan language of Virginia. The genus includes 17–19 species of deciduous trees with pinnately compound leaves and big nuts...

, sweet chestnut
Chestnut , some species called chinkapin or chinquapin, is a genus of eight or nine species of deciduous trees and shrubs in the beech family Fagaceae, native to temperate regions of the Northern Hemisphere. The name also refers to the edible nuts they produce.-Species:The chestnut belongs to the...

 and sweetfern (Comptonia), and also some herbaceous
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...

 plants such as nettle
Nettles constitute between 24 and 39 species of flowering plants of the genus Urtica in the family Urticaceae, with a cosmopolitan though mainly temperate distribution. They are mostly herbaceous perennial plants, but some are annual and a few are shrubby...


The word catkin is a calque
In linguistics, a calque or loan translation is a word or phrase borrowed from another language by literal, word-for-word or root-for-root translation.-Calque:...

 from the Dutch
Dutch language
Dutch is a West Germanic language and the native language of the majority of the population of the Netherlands, Belgium, and Suriname, the three member states of the Dutch Language Union. Most speakers live in the European Union, where it is a first language for about 23 million and a second...

 katteken, meaning "kitten", on account of the resemblance to a kitten
A kitten is a juvenile domesticated cat.The young of big cats are called cubs rather than kittens. Either term may be used for the young of smaller wild felids such as ocelots, caracals, and lynx, but "kitten" is usually more common for these species....

's tail. Ament is from the Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 amentum, meaning "thong" or "strap".