Birch

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Birch
Temporal range: Ypresian–Recent
Betula pendula 001.jpg
Silver birch
Scientific classification Red Pencil Icon.png
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fagales
Family: Betulaceae
Subfamily: Betuloideae
Genus: Betula
L.
Subgenera
  • Betulenta
  • Betulaster
  • Neurobetula
  • Betula
  • Chamaebetula
Areal bereza.png
Range of Betula
Synonyms [1]
  • BetulasterSpach
  • ApterocaryonOpiz
  • ChamaebetulaOpiz

A birch is a thin-leaved deciduous hardwood tree of the genus Betula ( /ˈbɛtjʊlə/ ), [2] in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus Betula contains 30 to 60 known taxa of which 11 are on the IUCN 2011 Red List of Threatened Species. They are a typically rather short-lived pioneer species widespread in the Northern Hemisphere, particularly in northern areas of temperate climates and in boreal climates. [3]

Contents

Description

The front and rear sides of a piece of birch bark Birch bark front rear.jpg
The front and rear sides of a piece of birch bark

Birch species are generally small to medium-sized trees or shrubs, mostly of northern temperate and boreal climates. The simple leaves are alternate, singly or doubly serrate, feather-veined, petiolate and stipulate. They often appear in pairs, but these pairs are really borne on spur-like, two-leaved, lateral branchlets. [4] The fruit is a small samara, although the wings may be obscure in some species. They differ from the alders (Alnus, other genus in the family) in that the female catkins are not woody and disintegrate at maturity, falling apart to release the seeds, unlike the woody, cone-like female alder catkins.

The bark of all birches is characteristically marked with long, horizontal lenticels, and often separates into thin, papery plates, especially upon the paper birch. Distinctive colors give the common names gray, white, black, silver and yellow birch to different species.

The buds, forming early and full-grown by midsummer, are all lateral, without a terminal bud forming; the branch is prolonged by the upper lateral bud. The wood of all the species is close-grained with a satiny texture and capable of taking a fine polish; its fuel value is fair.

Flower and fruit

The flowers are monoecious, opening with or before the leaves. Once fully grown, these leaves are usually 3–6 millimetres (1814 in) long on three-flowered clusters in the axils of the scales of drooping or erect catkins or aments. Staminate catkins are pendulous, clustered, or solitary in the axils of the last leaves of the branch of the year or near the ends of the short lateral branchlets of the year. They form in early autumn and remain rigid during the winter. The scales of the mature staminate catkins are broadly ovate, rounded, yellow or orange color below the middle, and dark chestnut brown at apex. Each scale bears two bractlets and three sterile flowers, each flower consisting of a sessile, membranous, usually two-lobed, calyx. Each calyx bears four short filaments with one-celled anthers or strictly, two filaments divided into two branches, each bearing a half-anther. Anther cells open longitudinally. The pistillate segments are erect or pendulous, and solitary, terminal on the two-leaved lateral spur-like branchlets of the year. The pistillate scales are oblong-ovate, three-lobed, pale yellow-green often tinged with red, becoming brown at maturity. These scales bear two or three fertile flowers, each flower consisting of a naked ovary. The ovary is compressed, two-celled, and crowned with two slender styles; the ovule is solitary. Each scale bears a single small, winged nut that is oval, with two persistent stigmas at the apex.

Taxonomy

Subdivision

Betula species are organised into five subgenera.

Birch leaves DosenmoorBirken1.jpg
Birch leaves
Birches native to Europe and Asia include
  1. Betula albosinensis – Chinese red birch (northern + central China)
  2. Betula alnoides – alder-leaf birch (China, Himalayas, northern Indochina)
  3. Betula ashburneri – (Bhutan, Tibet, Sichuan, Yunnan Provinces in China)
  4. Betula baschkirica – (eastern European Russia)
  5. Betula bomiensis – (Tibet)
  6. Betula browicziana – (Turkey and Georgia)
  7. Betula calcicola – (Sichuan + Yunnan Provinces in China)
  8. Betula celtiberica – (Spain)
  9. Betula chichibuensis – (Chichibu region of Japan) [5]
  10. Betula chinensis – Chinese dwarf birch (China, Korea)
  11. Betula coriaceifolia – (Uzbekistan)
  12. Betula corylifolia – (Honshu Island in Japan)
  13. Betula costata – (northeastern China, Korea, Primorye region of Russia)
  14. Betula cylindrostachya – (Himalayas, southern China, Myanmar)
  15. Betula dahurica – (eastern Siberia, Russian Far East, northeastern China, Mongolia, Korea, Japan)
  16. Betula delavayi – (Tibet, southern China)
  17. Betula ermanii – Erman's birch (eastern Siberia, Russian Far East, northeastern China, Korea, Japan)
  18. Betula falcata – (Tajikistan)
  19. Betula fargesii – (Chongqing + Hubei Provinces in China)
  20. Betula fruticosa – (eastern Siberia, Russian Far East, northeastern China, Mongolia, Korea, Japan)
  21. Betula globispica – (Honshu Island in Japan)
  22. Betula gmelinii – (Siberia, Mongolia, northeastern China, Korea, Hokkaido Island in Japan)
  23. Betula grossa – Japanese cherry birch (Japan)
  24. Betula gynoterminalis – (Yunnan Province in China)
  25. Betula honanensis – (Henan Province in China)
  26. Betula humilis or Betula kamtschatica – Kamchatka birch platyphylla (northern + central Europe, Siberia, Kazakhstan, Xinjiang, Mongolia, Korea)
  27. Betula insignis – (southern China)
  28. Betula karagandensis – (Kazakhstan)
  29. Betula klokovii – (Ukraine)
  30. Betula kotulae – (Ukraine)
  31. Betula luminifera – (China)
  32. Betula maximowicziana – monarch birch (Japan, Kuril Islands)
  33. Betula medwediewii – Caucasian birch (Turkey, Iran, Caucasus)
  34. Betula megrelica – (Republic of Georgia)
  35. Betula microphylla – (Siberia, Mongolia, Xinjiang, Kazakhstan, Kyrgyzstan, Uzbekistan)
  36. Betula nana – dwarf birch (northern + central Europe, Russia, Siberia, Greenland, Northwest Territories of Canada))
  37. Betula pendula – silver birch (widespread in Europe and northern Asia; Morocco; naturalized in New Zealand and scattered locations in US + Canada)
  38. Betula platyphylla – (Betula pendula var. platyphylla)—Siberian silver birch (Siberia, Russian Far East, Manchuria, Korea, Japan, Alaska, western Canada)
  39. Betula potamophila – (Tajikistan)
  40. Betula potaninii – (southern China)
  41. Betula psammophila – (Kazakhstan)
  42. Betula pubescens – downy birch, also known as white, European white or hairy birch (Europe, Siberia, Greenland, Newfoundland; naturalized in scattered locations in US)
  43. Betula raddeana – (Caucasus)
  44. Betula saksarensis – (Khakassiya region of Siberia)
  45. Betula saviczii – (Kazakhstan)
  46. Betula schmidtii – (northeastern China, Korea, Japan, Primorye region of Russia)
  47. Betula sunanensis – (Gansu Province of China)
  48. Betula szechuanica – (Betula pendula var. szechuanica)—Sichuan birch (Tibet, southern China)
  49. Betula tianshanica – (Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan, Xinjiang, Mongolia)
  50. Betula utilis – Himalayan birch (Afghanistan, Central Asia, China, China, Tibet, Himalayas)
  51. Betula wuyiensis – (Fujian Province of China)
  52. Betula zinserlingii – (Kyrgyzstan)

Note: many American texts have B. pendula and B. pubescens confused, though they are distinct species with different chromosome numbers.

Birches native to North America include
  1. Betula alleghaniensis – yellow birch (B. lutea) (eastern Canada, Great Lakes, upper eastern US, Appalachians)
  2. Betula caerulea – blue birch (northeast of North America)
  3. Betula cordifolia – mountain paper birch (eastern Canada, Great Lakes, New England US)
  4. Betula glandulosa – American dwarf birch (Siberia, Mongolia, Russian Far East, Alaska, Canada, Greenland, mountains of western US and New England, Adirondacks)
  5. Betula lenta – sweet birch, cherry birch, or black birch (Quebec, Ontario, eastern US)
  6. Betula michauxii – Newfoundland dwarf birch (Newfoundland, Labrador, Quebec, Nova Scotia)
  7. Betula minor – dwarf white birch (eastern Canada, mountains of northern New England and Adirondacks)
  8. Betula murrayana – Murray's birch (Great Lakes endemic)
  9. Betula nana – dwarf birch or bog birch (also in northern Europe and Asia)
  10. Betula neoalaskana – Alaska paper birch also known as Alaska birch or Resin birch (Alaska and northern Canada)
  11. Betula nigra – river birch or black birch (eastern US)
  12. Betula occidentalis – water birch or red birch (B. fontinalis) (Alaska, Yukon, Northwest Territories, western Canada, western US)
  13. Betula papyrifera – paper birch, canoe birch or American white birch (Alaska, most of Canada, northern US)
  14. Betula populifolia – gray birch (eastern Canada, northeastern US)
  15. Betula pumila – swamp birch (Alaska, Canada, northern US)
  16. Betula uber – Virginia round-leaf birch (southwestern Virginia)

Etymology

The common name birch comes from Old English birce, bierce, from Proto-Germanic *berk-jōn (cf. German Birke, West Frisian bjirk), an adjectival formation from *berkōn (cf. Dutch berk, Low German Bark, Danish birk, Norwegian bjørk), itself from the Proto-Indo-European root *bʰerHǵ- ~ bʰrHǵ-, which also gave Lithuanian béržas, Latvian Bērzs, Russian berëza, Ukrainian beréza, Albanian bredh ‘fir’, Ossetian bærz(æ), Sanskrit bhurja, Polish brzoza, Latin fraxinus ‘ash (tree)’. This root is presumably derived from *bʰreh₁ǵ- ‘to shine, whiten’, in reference to the birch's white bark. The Proto-Germanic rune berkanan is named after the birch.

The generic name betula is from Latin, which is a diminutive borrowed from Gaulish betua (cf. Old Irish bethe, Welsh bedw).

Ecology

Birch trees by a river in Hankasalmi, Finland Hankasalmi stream.jpg
Birch trees by a river in Hankasalmi, Finland
A stand of birch trees Stand of birch trees.jpg
A stand of birch trees
A birch tree in autumn Sugise margid.jpg
A birch tree in autumn

Birches often form even-aged stands on light, well-drained, particularly acidic soils. They are regarded as pioneer species, rapidly colonizing open ground especially in secondary successional sequences following a disturbance or fire. Birches are early tree species to become established in primary successions, and can become a threat to heathland if the seedlings and saplings are not suppressed by grazing or periodic burning. Birches are generally lowland species, but some species, such as Betula nana , have a montane distribution. In the British Isles, there is some difference between the environments of Betula pendula and Betula pubescens, and some hybridization, though both are "opportunists in steady-state woodland systems". Mycorrhizal fungi, including sheathing (ecto)mycorrhizas, are found in some cases to be beneficial to tree growth. [6]

A large number of lepidopteran insects feed on birch foliage.

Uses

Birch plywood Birke Multiplex.JPG
Birch plywood
Finnish bath broom called vihta, braided from birch twigs Vihtoja.jpg
Finnish bath broom called vihta, braided from birch twigs

Because of the hardness of birch, it is easier to shape it with power tools; it is quite difficult to work it with hand tools. [7]

Cultivation

White-barked birches in particular are cultivated as ornamental trees, largely for their appearance in winter. The Himalayan birch, Betula utilis , especially the variety or subspecies jacquemontii, is among the most widely planted for this purpose. It has been cultivated since the 1870s, and many cultivars are available, including 'Doorenbos', 'Grayswood Ghost' and 'Silver Shadow'; 'Knightshayes' has a slightly weeping habit. Other species with ornamental white bark include Betula ermanii , Betula papyrifera , Betula pendula and Betula raddeana . [11]

Medical

Approved topical medicine

In the European Union, a prescription gel containing birch bark extract (commercial name Episalvan, betulae cortex dry extract (5-10 : 1); extraction solvent: n-heptane 95% (w/w)) was approved in 2016 for the topical treatment of minor skin wounds in adults. [12] Although its mechanism of action in helping to heal injured skin is not fully understood, birch bark extract appears to stimulate the growth of keratinocytes which then fill the wound. [12] [13]

Research and traditional medicine

Preliminary research indicates that the phytochemicals, betulin and possibly other triterpenes, are active in Episalvan gel and wound healing properties of birch bark. [13]

Over centuries, birch bark was used in traditional medicine practices by North American indigenous people for treating superficial wounds by applying bark directly to the skin. [13] Splints made with birch bark were used as casts for broken limbs in the 16th century. [14]

Paper

A birch bark inscription excavated from Novgorod, circa 1240-1260 Birch bark document 210.jpg
A birch bark inscription excavated from Novgorod, circa 1240–1260

Wood pulp made from birch gives relatively long and slender fibres for a hardwood. The thin walls cause the fibre to collapse upon drying, giving a paper with low bulk and low opacity. The birch fibres are, however, easily fibrillated and give about 75% of the tensile strength of softwood.[ clarification needed ] [15] The low opacity makes it suitable for making glassine.

In India, the birch (Sanskrit: भुर्ज, bhurja) holds great historical significance in the culture of North India, where the thin bark coming off in winter was extensively used as writing paper. Birch paper (Sanskrit: भुर्ज पत्र, bhurja patra) is exceptionally durable and was the material used for many ancient Indian texts. [16] [17] The Roman period Vindolanda tablets also use birch as a material on which to write and birch bark was used widely in ancient Russia as notepaper (beresta) and for decorative purposes and even making footwear (lapti) and baskets.

Tonewood

Baltic birch is among the most sought-after wood in the manufacture of speaker cabinets. Birch has a natural resonance that peaks in the high and low frequencies, which are also the hardest for speakers to reproduce.[ citation needed ] This resonance compensates for the roll-off of low and high frequencies in the speakers, and evens the tone. Birch is known for having "natural EQ".

Drums are often made from birch. Prior to the 1970s, it was one of the most popular drum woods. Because of the need for greater volume and midrange clarity, drums were made almost entirely from maple until recently,[ clarification needed ] when advances in live sound reinforcement and drum microphones have allowed the use of birch in high-volume situations. Birch drums have a natural boost in the high and low frequencies, which allows the drums to sound fuller.

Birch wood is sometimes used as a tonewood for semiacoustic and acoustic guitar bodies, and occasionally for solid-body guitar bodies. It is also a common material used in mallets for keyboard percussion.

Culture

Birches have spiritual importance in several religions, both modern and historical. In Celtic cultures, the birch symbolises growth, renewal, stability, initiation, and adaptability because it is highly adaptive and able to sustain harsh conditions with casual indifference. Proof of this adaptability is seen in its easy and eager ability to repopulate areas damaged by forest fires or clearings. Birches are also associated with Tír na nÓg , the land of the dead and the Sidhe , in Gaelic folklore, and as such frequently appear in Scottish, Irish, and English folksongs and ballads in association with death, or fairies, or returning from the grave. The leaves of the silver birch tree are used in the festival of St George, held in Novosej and other villages in Albania. [18]

The birch is New Hampshire's state tree and the national tree of Finland and Russia. The yellow birch is the official tree of the province of Quebec (Canada). The birch is a very important element in Russian culture and represents the grace, strength, tenderness and natural beauty of Russian women as well as the closeness to nature of the Russians. [19] It's associated with marriage and love. [20] There are numerous folkloric Russian songs in which the birch tree occurs. The Ornäs birch is the national tree of Sweden. The Czech word for the month of March, Březen, is derived from the Czech word bříza meaning birch, as birch trees flower in March under local conditions. The silver birch tree is of special importance to the Swedish city of Umeå. In 1888, the Umeå city fire spread all over the city and nearly burnt it down to the ground, but some birches, supposedly, halted the spread of the fire. To protect the city against future fires, wide avenues were created, and these were lined with silver birch trees all over the city. Umeå later adopted the unofficial name of "City of the Birches (Björkarnas stad)". Also, the ice hockey team of Umeå is called Björklöven , translated to English "The Birch Leaves".

"Swinging" birch trees was a common game for American children in the nineteenth century. American poet Lucy Larcom's "Swinging on a Birch Tree" celebrates the game. [21] The poem inspired Robert Frost, who pays homage to the act of climbing birch trees in his more famous poem, "Birches". [22] Frost once told "it was almost sacrilegious climbing a birch tree till it bent, till it gave and swooped to the ground, but that's what boys did in those days". [23]

See also

Related Research Articles

Alder Genus of flowering plants in the birch family Betulaceae

Alder is the common name of a genus of flowering plants, Alnus, belonging to the birch family Betulaceae. The genus comprises about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few species extending into Central America, as well as the northern and southern Andes.

<i>Betula pendula</i> Species of birch

Betula pendula, commonly known as silver birch, warty birch, European white birch, or East Asian white birch, is a species of tree in the family Betulaceae, native to Europe and parts of Asia, though in southern Europe, it is only found at higher altitudes. Its range extends into Siberia, China, and southwest Asia in the mountains of northern Turkey, the Caucasus, and northern Iran. It has been introduced into North America, where it is known as the European white birch, and is considered invasive in some states in the United States and parts of Canada. The tree can also be found in more temperate regions of Australia.

<i>Betula pubescens</i> Species of birch

Betula pubescens, commonly known as downy birch and also as moor birch, white birch, European white birch or hairy birch, is a species of deciduous tree, native and abundant throughout northern Europe and northern Asia, growing farther north than any other broadleaf tree. It is closely related to, and often confused with, the silver birch, but grows in wetter places with heavier soils and poorer drainage; smaller trees can also be confused with the dwarf birch.

<i>Betula papyrifera</i> Species of flowering plant in the birch family Betulaceae

Betula papyrifera is a short-lived species of birch native to northern North America. Paper birch is named for the tree's thin white bark, which often peels in paper like layers from the trunk. Paper birch is often one of the first species to colonize a burned area within the northern latitudes, and is an important species for moose browsing. The wood is often used for pulpwood and firewood.

<i>Betula alleghaniensis</i> Species of flowering plant in the birch family Betulaceae

Betula alleghaniensis, the yellow birch, golden birch, or swamp birch, is a large and important lumber species of birch native to northeastern North America. Its vernacular names refer to the golden color of the tree's bark. The name Betula lutea was used expansively for this tree but has now been replaced.

<i>Betula lenta</i> Species of plant

Betula lenta is a species of birch native to eastern North America, from southern Maine west to southernmost Ontario, and south in the Appalachian Mountains to northern Georgia.

<i>Eriophorum</i> Genus of flowering plants in the sedge family Cyperaceae

Eriophorum is a genus of flowering plants in the family Cyperaceae, the sedge family. They are found throughout the arctic, subarctic, and temperate portions of the Northern Hemisphere in acid bog habitats, being particularly abundant in Arctic tundra regions.

<i>Betula nana</i> Species of flowering plant

Betula nana, the dwarf birch, is a species of birch in the family Betulaceae, found mainly in the tundra of the Arctic region.

Birch sap

Birch sap,birch water or birch juice is the sap directly tapped from birch trees, Betula pubescens, Betula pendula, Betula lenta, Betula papyrifera, and Betula fontinalis.

<i>Betula neoalaskana</i> Species of birch

Betula neoalaskana or Alaska birch, also known as Alaska paper birch or resin birch, is a species of birch native to Alaska and northern Canada. Its range covers most of interior Alaska, and extends from the southern Brooks Range to the Chugach Range in Alaska, including the Turnagain Arm and northern half of the Kenai Peninsula, eastward from Norton Sound through the Yukon, Northwest Territories, British Columbia, Alberta, Saskatchewan, Manitoba, southern Nunavut, and into northwestern Ontario.

<i>Betula populifolia</i> Species of birch

Betula populifolia is a deciduous tree native to eastern North America.

<i>Betula occidentalis</i> Species of birch

Betula occidentalis, the water birch or red birch, is a species of birch native to western North America, in Canada from Yukon east to western Ontario and southwards, and in the United States from eastern Washington east to western North Dakota, and south to eastern California, northern Arizona and northern New Mexico, and southwestern Alaska. It typically occurs along streams in mountainous regions.

<i>Neottia</i> Genus of orchids

Neottia is a genus of orchids. The genus now includes the former genus Listera, commonly known as twayblades referring to the single pair of opposite leaves at the base of the flowering stem. The genus is native to temperate, subarctic and arctic regions across most of Europe, northern Asia, and North America, with a few species extending into subtropical regions in the Mediterranean, Indochina, the southeastern United States, etc.

<i>Betula cordifolia</i> Species of birch

Betula cordifolia, the mountain paper birch is a birch species native to Eastern Canada and the Northeastern United States. Until recently it was considered a variety of Betula papyrifera, with which it shares many characteristics, and it was classified as B. papyrifera var. cordifolia (Regel) Fern.

<i>Betula utilis</i> Species of birch

Betula utilis, the Himalayan birch, is a deciduous tree native to the Western Himalayas, growing at elevations up to 4,500 m (14,800 ft). The Latin specific epithet utilis means "useful", and refers to the many uses of the different parts of the tree. The white, paper-like bark was used in ancient times for writing Sanskrit scriptures and texts. It is still used as paper for the writing of sacred mantras, with the bark placed in an amulet and worn for protection. Selected varieties are used for landscaping throughout the world, even while some areas of its native habitat are being lost due to overuse of the tree for firewood.

<i>Alnus alnobetula</i> Species of tree

Alnus alnobetula is a common tree widespread across much of Europe, Asia, and North America. Many sources refer to it as Alnus viridis, the green alder, but botanically this is considered an illegitimate name synonymous with Alnus alnobetula subsp. fruticosa.

<i>Agyneta</i> Genus of spiders

Agyneta is a genus of dwarf spiders that was first described by J. E. Hull in 1911.

Gnathonarium is a genus of dwarf spiders that was first described by Ferdinand Anton Franz Karsch in 1881.

<i>Myzia oblongoguttata</i> Species of beetle

Myzia oblongoguttata, commonly known as the striped ladybird, is a species of beetle in family Coccinellidae. It is found in the Palearctic.

References

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  2. Sunset Western Garden Book, 1995:606–607
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  4. Keeler, Harriet L. (1900). Our Native Trees and How to Identify Them. New York: Charles Scribner's Sons. pp.  295–297.
  5. Kinver, Mark (30 September 2015). "UK team germinates critically endangered Japanese birch". BBC News . BBC . Retrieved 30 September 2015.
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  8. "Birch Tar – How to collect it". Archived from the original on February 27, 2008.
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  10. Joyce, Daniel. "Birch Seed Leaves". reapermini.com. Archived from the original on 2010-12-31. Retrieved 2010-04-09.
  11. Bartlett, Paul (2015). "White-barked birches". The Plantsman. New Series. 14 (3): 146–151.
  12. 1 2 "Episalvan". European Medicines Agency. 5 February 2016. Retrieved 29 October 2020.
  13. 1 2 3 Ebeling, Sandra; Naumann, Katrin; Pollok, Simone; Wardecki, Tina; Vidal-y-Sy, Sabine; Nascimento, Juliana M.; Boerries, Melanie; Schmidt, Gudula; Brandner, Johanna M.; Merfort, Irmgard (2014-01-22). Simon, Michel (ed.). "From a traditional medicinal plant to a rational drug: Understanding the clinically proven wound healing efficacy of birch bark extract". PLOS ONE. 9 (1): e86147. Bibcode:2014PLoSO...986147E. doi:10.1371/journal.pone.0086147. ISSN   1932-6203. PMC   3899119 . PMID   24465925.
  14. William Arthur Clark (January 1, 1937). "History of fracture treatment up to the sixteenth century". The Journal of Bone and Joint Surgery. 19 (1): 61–62. Archived from the original on December 3, 2013. Retrieved December 2, 2013. Another method cited was that of splints made of birch bark soaked in water until quite soft. They were then carefully fitted to the limb and tied with bark thongs. On drying, they became stiff and firm. There is no record of the use of extension, but, nevertheless, very few crippled and deformed Indians were to be seen.
  15. Nanko, Hiroki; Button, Alan; Hillman, Dave (2005). The World of Market Pulp. USA: WOMP, LLC. pp. 192–195. ISBN   0-615-13013-5.
  16. Sanjukta Gupta, "Lakṣmī Tantra: A Pāñcarātra Text", Brill Archive, 1972, ISBN   90-04-03419-6. Snippet:... the text recommends that the bark of the Himalayan birch tree (bhurja-patra) should be used for scribbling mantras ...
  17. Amalananda Ghosh, "An Encyclopaedia of Indian Archaeology", BRILL, 1990, ISBN   90-04-09264-1. Snippet:... Bhurja-patra, the inner bark on the birch tree grown in the Himalayan region, was a very common writing material ...
  18. "Traditional celebrations in Novosej". RASP. Retrieved August 28, 2013.
  19. "The Birch: Russia's Tree | News & Info". kurochkaclothing.com. Retrieved 2018-09-24.
  20. 1932-1996., Weiss, Peg (1995). Kandinsky and Old Russia : the artist as ethnographer and shaman. Kandinsky, Wassily, 1866-1944. New Haven: Yale University Press. p.  36. ISBN   0300056478. OCLC   30701876.CS1 maint: numeric names: authors list (link)
  21. Pfileger, Pat. "Our Young Folks: Swinging on a Birch-Tree, by Lucy Larcom & Winslow Homer (1867)". Merry Coz.
  22. Fagan, Deirdre J. (2007). Critical Companion to Robert Frost: A Literary Reference to His Life and Work. Infobase Publishing. p. 42. ISBN   978-1-4381-0854-4 . Retrieved 10 November 2013.
  23. Parini, Jay (1999). Robert Frost: A Life . New York: Halt. p.  22. ISBN   0-8050-3181-2.

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