Taraxacum Weber
Dandelion.
Asteraceae (Compositae), daisy family.
Vegetative morphology. Plants perennial herbs; (3–)5–20(–30) cm high; with basal, simple, runcinate, leaves, scapose flowering stems bearing a single capitulum with yellow or pale yellow ligulate florets.; with milky juice. Taproot present. Caudex present. Vegetative, aerial, stem a small transition zone between roots and basal leaves. Leaves not heterophyllous (but sometimes very variable on the same plant); in a basal tuft, or basal in a rosette. Leaves patent, or erect. Leaves alternate; simple; existing for a single season or less. Petioles present, or absent; 0–40(–70) mm long; winged, or unwinged; glabrous. Leaf blade bases attenuate. Blades (15–)20–90(–120) mm long; 2.5–30 mm wide. Blades lanceolate, or oblanceolate, or obovate, or spatulate; flat; veins pinnate, or appearing single-veined. Blades adaxial surface glabrous. Blades abaxial surface glabrous. Blade margins lobed. Blade margins entire (or subentire; without dentations on the runcinate lobes); with teeth all around the blade, or toward the apex; degree of incision 50–95 %. Leaf apices acuminate, or acute.
Reproductive morphology. Plants bisexual, or agamospermic (pollen lacking). Flowering stems present. Flowering stems without leaves; glabrous, or hairy (near the capitulum). Flowering stem hairs woolly; simple (and floccose near the capitulum); longer than the diameter of the flowering stem; white or translucent (if applicable). Inflorescence a solitary head. Capitula 8–30 mm deep. Capitula 7–40 mm wide. Inflorescence not elongating as the fruit matures (it is the beaks of the achenes that become long and slender and carry the pappus higher in the captiulum). Pedicels absent. Involucral bracts present; number of rows 2–3. Outer involucral bracts blade surface flat; mostly green (often with two conspicuous lines); lying adjacent to the flowers; lanceolate, or ovate; glabrous; 2.5–11 mm high; 0.8–3.5 mm wide. Inner involucral bracts apex prominently horned, or sometimes callose, but without a prominent horn, or with or without horns or calloses, or entire; linear, or lanceolate; margins wide, scarious for at least one quarter of the bract, or at the most with narrow and scarious, less than one quarter of the bract; 8–20 mm high; 1.5–3 mm wide. With only ray florets. Flowers per inflorescence 30–60; zygomorphic. Calyx modified to a pappus. Calyx accrescent. Pappus with a single row of hairs. Pappus yellowish, or whitish. Ray floret pappus 4–8 mm long. Petals fused; 5; green (?), or white, or yellow; with contrasting markings, or without contrasting markings. Corolla ligulate. Ray florets 25–60. Ray florets limb 7.5–18 mm long; 0.8–2.5 mm wide. Stamens 5. Anthers yellow; (1.2–)3–4 mm long. Gynoecia inferior. Carpels syncarpous; 2. Styles 1. Stigmas per style 2; strap-like lobes. Placentation basal. Ovules 1. Fruit sessile. Fruit with calyx persisting; dry; cypselas; obovate; indehiscent. Fruit 3–4.5 mm long; 0.7–1.1 mm wide; yellowish, or black, or red, or straw coloured; glabrous; surface appearing veinless, or venation ribbed. Cypselas surface spinulose (at least at the apex); in upper half, or throughout. Cypselas beak at least 3/4 of the length of the body; beak stout, not, or scarcely longer than the body, or slender, often much longer than the body. Seeds 1.
Chromosome information. 2n = 16, 24, 32, 40.
Distribution. Common.
Indigenous knowledge. Porsild (1953) stated that the tender, young,
leaves of all species, especially when blanched, make and excellent salad and
throughout the summer the leaves may be used as a potherb.
(Burt 2000)
stated that there is no evidence that dandelions were used by Inuit around
Bathurst Inlet.
An Algonquin legend relates the story of Shawondesee, the
fat lazy south wind. One day he observed a dandelion in the form of a beautiful
golden-haired maiden on the meadow near him, but he was too lazy to pursue her.
In a few days, he returned, and saw a bent old woman with grizzled white hair.
Disappointed, he heaved a tremendous sigh, and observed the old woman’s
white hair fly away on the breeze. In the spring, the south wind sill sighs for
the lost beauty who might have been his Small and Catling (1999).
The
Iroquis ascribed sexual symbolism to dandelion roots. Roots with a side root
reminiscent of the male sexual organ were tossed backwards while saying the name
of one’s desired love. Alternatively, roots growing intertwined were
boiled, and the water used to wash one’s face and fingers in the
expectation that this would make one sexually irresistible (Small and Catling
1999).
Economic uses. Medicinal uses. Small and Catling (1999)
reported that as a medicinal plant dandelion has been used at least since the
time of the Arabian physicians of the 10th and 11th centuries. Root extracts
were once used extensively as a diuretic (to promote urination), and are still
sometimes so employed. Dandelion has also been said to be useful for treating
jaundice and other liver ailments. Both of these medicinal properties seem to
trace to the Doctrine of Signatures, whereby aspects of plants are said to
signal their medicinal uses. The yellowness of dandelion flowers was interpreted
as a sign that jaundice (which causes yellow coloration) and other liver
diseases could be treated. The juiciness of the dandelion suggestive of water
retention, was interpreted as indicating usefulness as a diuretic. For most
people the only hazard of consuming dandelion is excessive urination. Overuse of
diuretics can lower the level of potassium ions and lead to muscular weakness
and constipation.
The bitter resin in the roots and shoots contains
taraxacin, taraxerin, taraxerol, taraxasterol, inulin, gluten, gum, potash,
choline, levulin and putin. The dried plant contains 2.8% tannins (Williams et
al. 1996).
Non-Medicinal uses. Dandelion has been consumed for
thousands of years as food. Almost all parts of the dandelion can be eaten. The
nutritive value of dandelion greens, particularly for vitamin C, is much higher
than that of most other salad plants. Dandelion is grown commercially as a food
plant in northern Europe. At least a dozen cultivars are available and much
tastier than commercial dandelion. In Canada, over 50 commercially sold
medicinal preparations contain dandelion (Small 1997).
There are indications
that seeds of dandelions were deliberately brought to North America by the
Mayflower pilgrims, quite possibly to grow as a garden plant. The dandelion has
been declared an endangered wildflower in England. (Small and Catling 1999).
Notes. The common name "dandelion" comes from the French dente de
lion which refers to the toothed leaves and translates as "tooth of the
lion" Burt (2000).
ManyTaraxacum species do not produce fertile
pollen, but produce their seed by pathenogensis (without fertilization). This
mechanism, which does not involve genetic exchange of material between two
plants results in minor variations persisting and leads to problems in plant
identification.
Along the arctic coast, most dandleion are associted with
soil that has been enriched by nesting birds, burrowing mammals, or humans. They
are common on bird nesting islands but, even there they tend to become establish
at the edge of traditional nests, where the incubating bird defecates over the
edge of thest. They also become established below traditional raptor next sites
on cliffs Burt (2000).
Porsild (1939) reported that the scapes in
Taraxacum during their life cycle often perform a series of
characteristic movements. In the early stages the heads with their short scapes
are hiddeNorth Americaong the rosette leaves. Later, when the heads are nearly
full grown but still firmly closed, they emerge because of the rapid elongation
of the scapes. The upper portion of the scape at first is sharply hooked and the
head at this stage is nodding, but when it opens the scape gradually straigthens
out. After flowering the entire scape bends downward so that the head often
touches the ground or is hiddeNorth Americaong the leaves. When the achenes are
ripe the scape once more becomes erect and at the same time grows to more than
double its former length. These movements are effected by the unequal
intercalary growth of the scape which derives its strength solely from epidermal
or sub-epidermal layers of collenchyma, without other mechanical tissue, the
only lignified parts being the walls of the vessels. The rigidity and supporting
strength of the scape is thus due to turgor pressure alone. If one attempts to
straigthen the sharply curved young scape by force it will bend sharply, but
will not reassume its curve. When the mature achenes have been shed, a process
that may take by a few minutes, the scapes almost immediately loses it turgor
and withers.
Porsild (1939) claimed his son had noted his son had noted that
most Taraxacum plants in North America have closed heads that is
apparently a further advance in apogamy. In plants where the heads remain closed
the second phase of curving does not occur and only elongation takes place.
The knowledge (and study) of Taraxacum is very uneven in different
regions. In some regions field investigations have been made by Taraxacum
specialists as in Iceland (Christiansen, 1942), Fennoscandia (Lindberg,
Dahlstedt, Haglund), and parts of Siberia and the Russian Far East (Tzvelev,
Yurtsev). From other areas the specialists have revised collections collected by
non-specialists as in Alaska, Greenland and the Norwegian arctic islands. For
northernorthern European Russia and Canada no thorough or remotely thorough
surveys seem to have been made.
and Sell in Tutin et al. (1976, Flora
Europaea 4) accepted 21 sections in Taraxacum for Europe but only six of
these reaches the arctic areas, in northern Europe or elsewhere. These six seem
to more or less encompass all the reported arctic groups and have been taken up
as a framework for the Panarctic Flora checklist. The sections are based mainly
on the works of Hugo Dahlstedt who seems to have been the only scientist
working thoroughly with Taraxacum and comparing them in most major areas
in the circumpolar zones, in Greenland, North America (especially Alaska),
northern Siberia and Russia, Northernorthern Europe, and Greenland. Scientists
working in more constricted areas have usually found the need for more sections
in their regions (e.g., Richards and Sell in Britain, see Stace (1977),
Christiansen (1942) in Iceland, partly Tzvelev in Russia) but have not checked
whether the sections proposed would function also outside their regions. For
this reason, the Panarctic Flora checklist suggested using Dahlsteds's broad
sections.
*Sect. Arctica Dahlst. Acta Fl. Suec. 1: 37. 1929.
Hultén (1950) and Hultén and Fries (1986) recognized two
widely distributed arctic sections in this affinity. In the Panarctic Flora
checklist, Tzvelev and Yurtsev recognize one narrow Eurasian and one wider
nearly circumpolar subsections. The difference is that the T.
kamtschaticum-alaskanum group is treated in Arctica by Tzvelev and
Yurtsev and in Glabra by Hultén. Richards and Sell (1976) included
Sect. Glabra in Sect. Arctica as one of its species groups. That
approach is proposed by the Panarctic Flora checklist.
Hultén (1950)
based his treatment for Alaska on Dahlstedt's fairly detailed study and only
recognized two Alaskan species in his sect. Arctica (T.
hyparcticum and T. phymatocarpum), or three when T.
kamtschaticum of Hultén's sect. Glabra is transferred. In the
Panarctic Flora checklist rather more species are recognized by Tzvelev and
Yurtsev, for the North American side. As there is probably no way yet to
reconcile the 'Russian' and 'North American' approaches, the 'Russian' treatment
is to be proposed accepted the Panarctic Flora checklist. Nomenclature that has
been used in North American taxa relevant to the eastern Canadian Arctic
Archipelago for this section:
Taraxacum holmenianum Sahlin
aggregate.
Taraxacum hyparcticum Dahlst.
Taraxacum phymatocarpum J. Vahl
Yutsev (personal
communication in 2001) claims that in the eastern Canadian Arctic Archipelago
(Banks, Victoria, Axel Heiberg and Ellesmere Islands) there is one more
(undescribed) species closely allied with T. tolmaczewii but with larger
heads, blackish stigmas and no pollen. It was included in T. pumilum
Dahlst. by Porsild (1957) and then transferred to T. arcticum (Porsild
1964), from which species it can be easily distinguished for example by the the
leaf dissection.
[Taraxacum sibiricum Dahlst. (1905),
Ark. Bot. 4, 8: 36. - Described from [Russian]. - 2n = 24 (Zhukova 1968, Tzvelev
and Zhukova 1986). The identity of the American populations with the Asian ones
needs confirmation. Porsild and Cody (1980) record pale yellow ligules for the
American plants under this name, whereas the Asian ones have deep yellow
ligules. (Yurtsev personal communication to the PAF
checklist).]
[Taraxacum alaskanum Rydb. aggregate (including
Taraxacum alaskanum Rydb. Bull. Torrey Bot. Club 28: 512. 1901. Described
from Northern Alaska. 2n=24, 32 (Tzvelev and Zhukova 1986). Taraxacum
alaskanum Rydb. is close to T. sibiricum according to Hultén
(1968) and not recorded from the Arctic Islands.
[Taraxacum
arcticum (Trautv.) Dahlst. aggregate (including Taraxacum
arcticum (Trautv.) Dahlst. (1905), Ark. Bot. 4, 8: 8. Basionym:
Taraxacum. vulgare Schrank var. arcticum Trautv. (1871), Tr. Peterb. Bot.
Sada 1, 1: 72. Described from Russia: Novaya Zemlya. 2n=40 (Zhukova 1968).
Records of T. arcticum from the eastern Canadian Arctic Archipelago
(Porsild 1964) are incorrect and relate to an undescribed species of the
subsection (Yutsev personal communication 2001).
*Sect. Borealia
Hand.-Mazz. (sect. Ceratophora (Dahlst.) Dahlst., non Meg.).
This
section includes the Taraxacum ceratophorum (Ledeb.) DC. aggregate that
contains
(1) Taraxacum arctogenum ['arctogena'?] Dahlst., Ark.
Bot. 5, 9: 26. - 1906. 2n=32.
(2) Taraxacum hyperboreum Dahlst. in
Ostenf., Skr. Chria. Vidensk.-Selsk. Skr., Math.-Nat. 8: 26. 1909.
Hultén's (1968) map suggests that Taraxacum ceratophorum
(Ledeb.) D.C. occurs in the islands of the Canadian Arctic Archipelago. He
described it as having leaves of various forms; all or at least some involucral
bracts with horn or tubercle below the apex; outer bracts mostly appressed and
broader than the inner ones. Hultén (1968) commented that T.
ceratophorum is composed of a large group of small taxa, which maintain
themselves as distinct units through seeds that are formed without
fertilization.
*Sect. Spectabilia (Dahlst.) Dahlst. Also
including the three proposed sections - Sect. Crocea M.P.Christ., Sect.
Naevosa M.P.Christ., and Sect. Macrodonta M.P.Christ. - based on
Icelandic variation but largely accepted by Richards/Sell, and Sect.
Celtica A.J.Richards.
Sect. Crocea M. Christ. Subsect.
Crocea (M. Christ.) Richards. Taraxacum croceum Dahlst. in
Anderss. and Hesselm. (1900), Bih. Kongl. Sv. Vetensk.-Akad. Handl. 26, 3, 1:
12. Synonym: T. lapponicum (Kihlm.) Hand.-Mazz.
*Sect.
Erythrosperma (H. Lindb.) Dahlst. Also including Sect. Fulva
M.P.Christ. based on Icelandic variation.
*Sect. Boreigena
Dahlst. ex G.E.Haglund.
*Sect. Taraxacum (Sect.
Ruderalia ). Also including Sect. Hamata H. Øllg. and Sect.
Subvulgaria M.P.Christ. (This section Included the T. officinale
agg.).
Of these sections, Arctica and Borealia have their main
variation in Northern Asia and the amphi-Beringian (or amphi-Pacific) regions.
Sect. Erythrosperma is mainly European and touches on the Arctic in a
very few places, one in northern Siberia.. The sections Spectabilia and
Boreigena have their focus in, respectively, the North Atlantic
surroundings and NW Europe. Section Taraxacum is very sparingly
represented in the Arctic and mainly as more or less casual ruderals. In this
section, continuous hybridization and segregation probably produces new
'biotypes' much more rapidly than it is possible to describe them.
Aiken
(June 2001) in a study of Taraxacum specimens from the eastern Canadian
Arctic observed a colour transition between developing achenes, that are dark
red, and more mature achenes that have faded to yellowish or straw colored and
concluded that achene colour is not reliable unless the achenes are fully
developed.
It is reported that weedy dandelion seeds from "the south" have
been deliberately introduced to some Arctic communities (B. Rose, personal
communication, 1986.). When weedy, southern dandelions are in flower at
anthesis, the involucral bracts are reflexed; those of the native taxa are
appressed, or spreading around the capitulum, but not reflexed at the same stage
of flowering.
Haglund (1943) provided the following key to Taraxacum
in Arctic Canada.
A. Outer phyllaries corniculate-appendages beneath the
apex.
B. Outer phyllaries broad, short to more or less broad-ovate.
c.
Flowers white. Achenes black.................T. hyparcticum Dahlst.
c. Flowers yellow. Achenes greenish black
d. Leaves entire to sparingly
lobed. .......T. phymatocarpum J. Vahl.
d. Leaves densely lobed.
Lobes deltoid, more or less dentateT. alaskanum Rydb.
B. Outer
phyllaries mostly narrower and longer, more or less
ovate-lanceolate to
lanceolate, rarely with short, mostly with long
to very long appendages
beneath the apex. Flowers yellow. Achenes sordid to
greenish straw-coloured,
to more or less reddish to reddish brown.
d. Lobes of the leaves more or
less long, more or less narrow. Petioles
usually bright
violet-red............................................T. lacerum
Greene
d. Lobes of the leaves broader, deltoid. Petioles pale. T.
hyperboreum Dahlst.
c. Achene more of less red with a narrow,
cylindrical beak..T. maleanun Dahlst.
d. Achenes reddish brown to
umbra-brown with a more of less short, conical beak.
e. Terminal lobes of
the leaves mostly more or less sort (triangular).
f. Leaves long, narrow,
lobes short, triangular, more or less
remote with sharp
points.....................T. pseudonorvegicum Dahlst.
f. Leaves
shorter, lobes broader, deltoid, more or less approximate,
less acute....
.................................................T. umbrinum Dahlst.
A. Outer phyllaries lacking appendages.
B. Achenes straw-yellow with a
conic-cylindrical beak about 1 mm long
......................................................T. lapponicum
Kihlm.
B. Achenes light brown with a hardly conspicuous or very short,
conical beak.........................................................T.
dentifolium G. Hagl.
In this treatment we have followed Haglund (1943)
in recognizing T. hyparcticum, a distinct High Arctic taxon with pale
creamy coloured relatively large flowers, and T. phymatocarpum with lemon
coloured flowers and distinct grey or black spinulose achenes. We recongize the
T. holmenianum aggreagate Sahlin ex Kierschn. treated in Porsild
(1957) as T. pumilum Dahlst. (Ark. Bot 4/8. 27. 1905) a later homenom of
T. pumilum Gaudichaud (Ann. Sci. Natur, ser. 1,5: 103. 1825). This is a
High Arctic taxon with deep chrome yellow flowers with dark stigmas, and usually
patent, deeply runicinate leaves, that sometimes have additional dentations on
the runcinate lobes and achenes that may be reddish during development but
become olivacious or straw coloured when mature. In extreme environments, or on
calcereous substrates this taxon sometimes develops small plants that have
predominently deltoid dentate leaves. [
While such plants are striking, and
were originally considered as a possibly undescribed taxon at the suggestion of
Yutsev (2001). It has been possible to find a series between typical T.
holmenianum from places like Ellesemere Island and the small plants from
calcareous sites on Banks and Melville Islands. Describing a new taxon does not
appear to be justified until more reasons for doing so can be found. - I wish!
Problems: No horns on bracts ever, and two dark stripes down the bracts, ligule
petals size and anther size, - could this be T. alaskanum?
The name T.
lacerum Greene used in Porsild (1957) is based on a type from Northern
British Columbia Upper Liard River, (Isotypeastern Canada?!) and has leaves
unlike plants from Baffin Island.
No reason for continuing to recognize
T. hyperboreum Dahlst. as distinct from plants that have gone under the
name T. lacerum based on a difference in leaf shape and petiole colour
appears to be justified as these characters are observed to be vary with local
environments.
The type of T. hyperboreum Type: King William Land:
Frits Johansen 98714. Bernard Harbour.
Do we have the type and does it have
horns? Could be a better name for T. lacerum.
The name T.
malteanum aggregate is used to cover the plants treated under the name T.
lapponicum Kilhm. by Haglund (1943) and (Porsild 1957) as it is doubtful
whether plants recognizing the type of that name occur outside Fennoscandinavia.
The name T. malteanum aggregate is used as it was the first in the new
species recognized by Haglund (1943) and the type is from Baffin Island, (Lake
Harbour), Kimmirut. The key provided by Haglund (1943) and the differences that
he attempted to explain merge when one attempts to apply the names to
collections in this aggregate. Much variation in leaf shape is observed, and
most specimens lack mature achenes. Very young achenes that are already a deep
red suggestinng that they will retain the red colour when mature are observed.
In 2002, dandelions where observed by Aiken in two towns on Baffin Island,
(Iqaluit and Kimmarut) and in a 60 km survey of the Soper River Valley, in one
only place in the tundra, i.e. at Willow Creek, which many people visit to
observe willows to 3.7 m tall.
There is a popular suggestion in Iqaluit that
at least some of the dandelions may have been introduced in packing straw by the
Hudson Bay company and it is known that some dandelions were introduced from the
south deliberately, by a family that has summer holiday in Saskatchewan. In
Iqaluit, on 14 July, 2002 there were conspicuously two different dandelions,
growing together and in flower at Apex, on Baffin Island. This was the former
site of the Hudson Bay company. The suggestion is that seeds from this site have
spread on the prevailing winds, and been helped to spread, into Iqaluit. The
progress of dandelions across town each year is being gleefully monitored by an
Iqaluit resident who knows they were introduced. One of the taxa observed at
Apex had yellow flowers 2–3 cm in diameter, the other had much more orange
yellow
flowers 1–2 cm in diameter. Vouchers of these were made and
residents requested for seed material.
In the town of Kimmarut, 12 July,
2002, the only dandelions were the ones with yellow flowers 2–3 cm in
diameter. They were only found immediately within the town within easy blowing
distance of the Hudson Bay Post that was established there in 1911. Hugland
(1943) cited Kimmarut (then Lake Harbour) as the type location of two on the
taxa he named (T. maltanum and T. russeolum; collections made by
M.O. Malte in 1927 and 1928). In 2002 specimens were vouchered and the leaf
variation was photographed.
Luc Brouilett (Personal Communication July,
2002) indicated that normally, in southern Quebec or in Saskatchewan, the most
likely introduced species would be T. officinale. Another possibility is
T. erythrosperma, and very recently only, "palustris" (but this is not a
candidate for Baffin Island). I cannot
envisage other possibilities, unless
the eastern Canadaoes came from areas where a species like T. lapponicum
was growing.
Illustrations. • Plant habit. Note patent and deeply runicinte leaves. N.W.T., Tuktoyaktuk. Plants growing on beach mud, 22 July 1981, J.M. Gillett 18775. CAN. • Close-up of plant. Taraxacum brachyceras plant in fine calcareous schist scree. Norway: Troms, Maalselv, Lappskaret. June 1978. Photo: J.S.Svendsen. Voucher in HbTROM. • Inflorescence setting seeds. Involucral bracts with well developed horns on the outer and inner involucral bracts. Manitoba, Churchill. Aiken and Brysting, 01009. CAN. • Close-up of cypselas. Cypselas (sometimes incorrectly called achenes) dull browinish, with scupturing at the apex and long beacks before the pappus hairs. Manitoba, Churchill. Aiken and Brysting, 01009. CAN. • Close-up of bud. Flowering head in bud with spreading, outer, involucral bracts. Nunavut, Baffin Island, Kimmarut, Soper Lake. These were the only dandelion seen along the edge of the lake. Aiken 02–070. CAN. • Close-up of bud. Flowering head in bud with outter involucral bracts beginning to reflex. Aiken 02–070. CAN. • Plants in Kimmirut. Plants growing in disturbed ground at the base of a power pole. Nunavut, Kimmirut, edge of hamlet. Aiken and Ilse, 02–070. CAN. • Plant with almost entire leaves. Plant with almost entire leaves. Nunavut, Baffin Island, Kirrimut. Aiken and Isles, 02–070. CAN. • Underside of flowering head. Underside of flowering head showing conspicuous stripes in the outer ligulate petals narrow membrancous margins on the involucaral bracts that have somewhat horn-like appendices on the apecies. Aiken 02070. CAN. • Leaf-shape diversity. Leaves from dandelion plants collected in Kimmirut (Lake Harbour) the type location for T. malteanum Dahlst and T. russeolum Dahlst Leaves vary in shape from almost entire to deeply runcinate. 02–070. Aiken CAN. • Close-up of involucral bracts.. Flowering head with horns on the involucral bracts, and dark stripes in the outter ligulate petals. Aiken and Ilse 02–070. CAN.
Cite this publication as: ‘S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, L.J. Gillespie, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, A.K. Brysting and H. Solstad. 1999 onwards. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 29th April 2003. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993, 1995, 2000) should also be cited (see References).
