Medicinal and Aromatic Plants—Industrial Profiles


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BOTANY OF TEA TREE
13
but several also occur in adjacent parts of Indonesia and Papua New Guinea and one
species, M. cajuputi, extends from Australia northwards to the Asian mainland. There
is one endemic species in Lord Howe Island, M. howeana, and three species in New
Caledonia (eight including the Callistemon species) of which M. quinquenervia also
occurs in eastern Australia and New Guinea. Within Myrtaceae, Melaleuca is
characterised by possession of the following combination of features: Shrubs or trees;
leaves spiral, decussate or ternate, small to medium-sized, the venation pinnate to
parallel; flowers in spikes or clusters or sometimes solitary, the basic floral unit being
a monad, dyad or triad; sepals 5 (rarely 0); petals 5; hypanthium fused to the ovary in
the proximal region only; stamens few to numerous, the filaments fused for part of
their length into 5 bundles, the anthers dorsifixed (or rarely basifixed) and versatile
with two parallel cells that open via longitudinal slits; ovary 3-celled, the ovules few to
numerous; fruit a capsule within an usually woody to subwoody fruiting hypanthium;
seeds with a thin testa, generally obovoid-oblong to obovoid, unwinged, the cotyledons
planoconvex to obvolute.
TEA TREE
Tea tree, Melaleuca alternifolia (
Plates 2

3
), is very closely related to M. linariifolia, and it
is not surprising that Maiden and Betche treated the plant as a variety of that species when
they described it in 1905. It belongs in the M. linariifolia species group of which there are
five currently accepted species: M. alternifolia, M. dissitiflora, M. linariifolia, M. linophylla
and M. trichostachya. Maiden & Betche distinguished their variety alternifolia as having
alternate leaves that are much narrower and usually shorter than those of M. linariifolia
sensu stricto and having its flowers (Plate 3) less densely arranged in the inflorescences.
Cheel considered that the differences between the two, taken with their apparent geographic
isolation, were sufficient justification for the variety to be raised to specific rank (Cheel
1924).
The first-described, and best known, species of the group is M. linariifolia; this was
described by Smith in 1797 from specimens collected in the Sydney region in 1795. M.
linariifolia is widely cultivated in Australia as it is hardy and forms an attractive large shrub
or small tree with masses of pure white flowers.
The next described species is M. trichostachya, described by Lindley in 1848 from
specimens collected by the explorer Thomas Mitchell in 1846 in subtropical Queensland.
Bentham, however, reduced M. trichostachya to a variety of M. linariifolia in 1867. Of the
recent taxonomists who have worked on Melaleuca, Bentham’s placement was followed by
Byrnes (1985) but Quinn et al. (1989), who studied the complex in more detail than did
Byrnes, recognised M. trichostachya as a distinct species. The remaining two species of the
group, M. linophylla and M. dissitiflora, were described in 1862 and 1863, respectively, by
the 19th Century Australian botanist, Ferdinand Mueller.
Geographically, the group is widespread and occurs in a correspondingly broad range of
climates. The distributions of the species are shown in 
Figure 1
. Given the occurrence of
terpinen-4-ol chemotypes in M. alternifolia, M. dissitiflora and M. linariifolia, it would
seem that there is scope for a more intensive survey of the M. linariifolia group to gain a
greater understanding of the chemotypes and their distributions. Then it would be possible
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part of The Gordon and Breach Publishing Group.

LYN A.CRAVEN
14
to consider the prospects for expanding the tea tree oil industry, presently centred upon M.
alternifolia in NE New South Wales, by growing other terpinen-4-ol rich genotypes in
regions to which they are suited climatically and edaphically, by introgressing novel genes
into M. alternifolia and M. linariifolia for crop improvement with the NE New South Wales
region, or by both means.
Morphologically, the species need to be studied further, in the case of the central Australian
representatives preferably with flowering and fruiting materials collected from the same
trees, so that more comprehensive and possibly more definitive circumscriptions can be
made. Until then, the species of the M. linariifolia species group can be distinguished by
means of the key given below.
Future systematic studies should not be restricted to morphological aspects. Molecular
systematics, based upon comparative studies of DNA, in particular will assist in establishing
the evolutionary relationships of the species. Butcher et al. (1995) studied chloroplast DNA
(cpDNA) variation in M. alternifolia, M. linariifolia and M. trichostachya and in part their
findings were that M. linariifolia and M. trichostachya were readily distinguished on cpDNA
Figure 1 Distributions of Melaleuca species. 1, M. alternifolia 
•; M. dissitiflora  . 2, M. linariifolia
•; M. linophylla  . 3, M. trichostachya •
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part of The Gordon and Breach Publishing Group.

BOTANY OF TEA TREE
15
data. They also found that cpDNA data supported an earlier suggestion based upon leaf
terpene data (Butcher et al. 1994) that hybridisation may have occurred between M.
alternifolia and M. linariifolia in the southern part of the former species’ range. Clearly, the
incorporation of molecular data into the systematic synthesis will enable us to devise much
more accurate and informative classifications than we have been able to do using
morphological data alone.
List of species of the M. linariifolia group, including their synonyms and type specimens
1.
Melaleuca alternifolia (Maiden & Betche) Cheel, J. Proc. Roy. Soc. New S. Wales
58:195 (1924). Melaleuca linariifolia var. alternifolia Maiden & Betche, Proc. Linn.
Soc. New S.Wales 29:742 (1905). Typus: New South Wales: Coffs Harbour to Grafton,
Nov. 1903, Maiden and Boorman s.n. (NSW, holo, n.v.).
2.
Melaleuca dissitiflora F.Muell., Fragm. 3:153 (1863). Myrtoleucodendron dissitiflorum
(F.Muell.) Kuntze, Revis. gen. pl. 241 (1891). Typus: Northern Territory: between
Bonney River and Mount Morphett, 1862, Stuart s.n. (MEL, holo, iso, n.v.).
3.
Melaleuca linariifolia Sm., Trans. Linn. Soc. London, Bot. 3:278 (1797).
Myrtoleucodendron linariifolium (Sm.) Kuntze, Revis. gen. pl. 241 (1891). Melaleuca
linariifolia var. typica Domin, Biblioth. Bot. 89:456 (1928), nom. inval Typus: New
South Wales: 1795, White s.n. (LINN, holo, n.v.).
Metrosideros hyssopifolia Cav., Icon. 4:20, t.336. f.1. (1797). Melaleuca hyssopifolia
(Cav.) Dum.Cours., Bot. cult. 2, 5:375 (1811). Typus: The illustration accompanying
the original description.
4.
Melaleuca linophylla F.Muell., Fragm. 3:115 (1862). Myrtoleucodendron linophyllum
(F.Muell.) Kuntze, Revis. gen. pl. 241 (1891). Typus: Western Australia: northwest,
1861, Gregory s.n. (MEL, holo, n.v.; BRI, K, iso, n.v.).
5.
Melaleuca trichostachya Lindl., in Mitchell, J. exped. trop. Australia 277 (1848).
Melaleuca linariifolia var. trichostachya (Lindl.) Benth., Fl. Austral. 3:141 (1867).
Myrtoleucodendron trichostachyum (Lindl.) Kuntze, Revis. gen. pl. 242 (1891). Typus:
Queensland: sandy bed of Belyando River, 16 Aug. 1846, Mitchell 224 (CGE, holo,
n.v.; K, MEL, NSW, iso, n.v.).
Key to the species of the M. linariifolia group
1. Leaves decussate
2. Ovules 85–120 per locule; capsule persisting within the fruiting hypanthium;
cotyledons planoconvex........................................................M. linariifolia
 
2. Ovules 25–45 per locule; capsule at length deciduous and the empty fruiting
hypanthium then persisting; cotyledons obvolute to almost planoconvex.............
................................................................................... M. trichostachya
1. Leaves spiral
 
3. Hypanthium glabrous or effectively so (if distinctly hairy, then stamens more than
12mm long)
 
4. Stamens up to 12mm long; capsule at length deciduous and the empty fruiting
hypanthium then persisting..........................................M. trichostachya
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part of The Gordon and Breach Publishing Group.

LYN A.CRAVEN
16
 4. Stamens more than 12mm long; capsule persisting within the fruiting
hypanthium...................................................................M. alternifolia
3. Hypanthium distinctly hairy
 5. Stamens 2.2–3.5mm long, 7–15 per bundle..............................M. linophylla
 5. Stamens 4mm or more long, 15–35 per bundle........................M. dissitiflora
CAJUPUT AND NIAOULI
It is ironic that, considering their prominent form and frequency in the landscape,
and their utility as sources of timber, paperbark and essential oils, the tropical and
subtropical tree species of Melaleuca, collectively known either as the M. leucadendra
group or the broad-leaved paperbarks, have proved so difficult for botanists to classify.
Numerous species and varieties have been proposed but presently it is considered
that there are 15 species in the group, the majority being medium to large trees although
a few are shrubs or small, poorly formed trees. The distributions of the species are
shown in 
Figures 2

5
.
An indication of the lack of appreciation of the taxonomic limits in the broad-leaved
paperbarks can be found in the number of type specimens applicable to this group of plants.
To date, there are 45 type specimens but only 15 accepted species, whereas in the M.
linariifolia group there are 6 types and 5 species. Bentham (1867) dealt with the confusing
array of names and specimens known to him by recognising only a single species in his
Flora Australiensis account of the genus, i.e. M. leucadendron. [The majority of authors
have used Linnaeus’ later spelling “leucadendron”; it was only in 1966 that the original
spelling “leucadendra” was re-established in the edition of the International Code of
Botanical Nomenclature published in that year (Lanjouw et al. 1966).] Bentham was followed
by most botanists, although some, notably Cheel (1917), endeavoured to partition the
variation into varieties.
Blake (1968) published an extremely detailed revision of the M. leucadendra group,
based upon his extensive field knowledge and an excellent appreciation of the discriminatory
value of indumentum (hair type) and floral morphology in development of a workable
taxonomy for this group of plants. The work by Blake has provided a sound basis for
subsequent research. Byrnes (1984, 1985, 1986) generally followed Blake’s treatment of
the paperbarks although he combined M. quinquenervia and M. viridiflora on the basis that
the two species overlapped in the quantitative key characters given by Blake (1968). Byrnes
(1984) described several new taxa in the group, notably a number at varietal level; presumably
in part this was an acknowledgment of the regional differentiation within some of the species
that had been more broadly defined by Blake. In the 1980’s, B.A.Barlow and co-workers
reworked the taxonomy of the group but, although several new taxa were recognised by
them (and a number of Byrnes’ were not), their results unfortunately have not been published
in a synthetic account.
The species from which cajuput oil is extracted, M. cajuputi (
Plate 4

18

19
) is
widespread and occurs from southeast Asia to northern Australia. However, the source of
commercial cajuput oil are populations apparently originating in a restricted part of
Indonesia and now cultivated more widely in both Indonesia and other parts of southeast
Asia. These populations belong to a distinct form of the species, M. cajuputi subsp. cajuputi.
Copyright © 1999 OPA (Overseas Publishers Association) N.V. Published by license under the Harwood Academic Publishers imprint,
part of The Gordon and Breach Publishing Group.

BOTANY OF TEA TREE
17
Figure 2 Distributions of Melaleuca species. 1, M. arcana. 2, M. argentea. 3, M. clarksonii. 4, M.
cornucopiae
It is tempting to consider that the wide distribution of the species is a direct result of the fact
that the species is of value for its therapeutic oil with man having carried the plant around to
cultivate it. Once established in cultivation locally, it could then become naturalised and
expand its range using natural means of dispersal. Barlow (1988) discussed patterns of
differentiation in species of the M. leucadendra group, especially their geographic
distributions. Barlow has recognised three subspecies within M. cajuputi: subsp. cajuputi,
subsp. cumingiana and subsp. platyphylla. He considered that the western subspecies of M.
cajuputi, subsp. cumingiana, represented a colonisation event across Wallace’s Line from
the east, an unusual event as most of the plant movements across this line have been from
the west. This subject was taken up by Lum (1994). Lum concluded that genetic data
supported the hypothesis that M. cajuputi had dispersed naturally westward. However, Lum’s
genetic data were derived from relatively few populations that do not sample the species
across its range adequately; further work is required before an unequivocal assessment can
be made.
Copyright © 1999 OPA (Overseas Publishers Association) N.V. Published by license under the Harwood Academic Publishers imprint,
part of The Gordon and Breach Publishing Group.

LYN A.CRAVEN
18
Figure 3 Distributions of Melaleuca species. 5, M. cajuputi subsp. cajuputi. 6, M. cajuputi subsp.
cumingiana. 7, M. cajuputi subsp. platyphylla
Copyright © 1999 OPA (Overseas Publishers Association) N.V. Published by license under the Harwood Academic Publishers imprint,
part of The Gordon and Breach Publishing Group.

BOTANY OF TEA TREE 19
The other species of the M. leucadendra group used as a source of essential oil is M.
quinquenervia (
Plate 5

21

23
), called niaouli in New Caledonia and the source of niaouli oil.
This species occurs naturally in eastern Australia, southern New Guinea (including the southeast
Papuan islands) and New Caledonia. It is cultivated for essential oil production in Madagascar
(Ramanoelina et al. 1992, 1994) and is naturalised in the southeastern United States. Although
M. quinquenervia could have arrived in New Caledonia from the southeast Papuan islands, it
is more likely that it dispersed there from eastern Australia. As with M. cajuputi, very little is
known about the degree of intraspecific variation. Molecular studies aimed at identifying
markers that can be used to circumscribe provenance are required. Such studies may then
enable light to be shed upon the origins of the New Caledonian population.
As far as future work on the M. leucadendra group is concerned, studies directed towards
finding additional macrocharacters for distinguishing M. cajuputi from M. quinquenervia
and M. viridiflora from M. quinquenervia need to be undertaken. Further investigations
into essential oils are likely to be of interest; M. viridiflora, for example, has commercial
potential as a source of methyl cinnamate from the oil (
Chapter 16
, this volume). Blake
(1968) noted some examples of hybridisation between species in the M. leucadendra group
and this needs further consideration. For example, is the difficulty in distinguishing M.
cajuputi from M. quinquenervia due to hybridisation, and is the occasional occurrence of
paper bark in the usually hard barked M. clarksonii due to hybridisation or is it part of the
intrinsic variation of the species? Molecular techniques are likely to provide additional
powerful tools in studying such questions.
List of species of the M. leucadendra group, including their synonyms and type specimens
1.
Melaleuca arcana S.T.Blake, Contr. Queensland Herb. 1:54, figs. 10, 15J. (1968).
Typus: Queensland: NW of Cooktown and W of Cape Bedford, Blake 20260 (BRI,
holo, n.v.).
Melaleuca leucadendron var. albida f. ruscifolia Cheel, in Ewart & Davies, Fl. N.
Territory 302 (1917). Melaleuca ruscifolia Sol. ex Cheel, in Ewart & Davies, Fl. N.
Territory 302 (1917), nom. inval. Typus: Queensland: Point Lookout, Banks & Solander
s.n. (NSW, holo, n.v.; BM, E, K, MEL, P, W, n.v., CANB, iso,).
2.
Melaleuca argentea W.Fitzg., J. Proc. Roy. Soc. Western Australia 3:187 (1918). Typus:
Western Australia: base of Mt. Bartlett, Sep. 1905, Fitzgerald 1258 (NSW, holo, n.v.;
n.v., PERTH, iso).
3.
Melaleuca cajuputi Powell.
3a.
Melaleuca cajuputi Powell subsp. cajuputi, Pharm. Roy. Coll. Physic. London (Transl.)
1809, 22 (1809). Myrtus saligna J.F.Gmel, Syst. nat. 793 (1791), nom. illeg., non
Burm.f. Melaleuca trinervis Buch.-Ham., Mem. Wern. Nat. Hist. Soc. 6:302 (1832),
nom. illeg., non Sm. in White. Melaleuca saligna (J.F.Gmel.) Blume, Mus. Bot. 1:66
(1849), nom. illeg., non Schauer. Melaleuca leucadendron var. cajuputi (Powell) Nied.,
Natürl. Pfl.Fam IV, 3. 7:95 (1893). Typus: Rumphius, Herb. Amboin. 2:76, t. 17, figs.
1, 2 (1741) (the figures and description).
Melaleuca minor Sm., in Rees, Cycl. 23, no. 2 (1812). Melaleuca leucadendron var.
minor (Sm.) Duthie, in Hooker, Fl. Brit. India 2:465 (1878). Typus: Indonesia: Ceram,
Amboina, Oct. 1796, Cbr. Smith 303 (LINN, holo, n.v.; BM, G, NSW, iso, n.v.).
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LYN A.CRAVEN
20
Figure 4 Distributions of Melaleuca species. 8, M. dealbata. 9, M. fluviatilis. 10, M. lasiandra. 11, M.
leucadendra. 12, M. nervosa subsp. crosslandiana. 13, M. nervosa subsp. nervosa
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part of The Gordon and Breach Publishing Group.

BOTANY OF TEA TREE
21
Figure 5 Distributions of Melaleuca species. 14, M. quinquenervia, 15, M. saligna, 16, M. sericea.
17, M. stenostachya. 18, M. viridiflora
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part of The Gordon and Breach Publishing Group.

LYN A.CRAVEN
22
Melaleuca viridiflora var. angustifolia Blume, Bijdr. fl. Ned. Ind. 1099 (1826).
Melaleuca angustifolia (Blume) Blume, Mus. Bot. 1:83 (1849), nom. illeg., non
Gaertn. Typus: Indonesia: Moluccas, Amboina, herb. Blume s.n. (L, holo, n.v.; BRI,
fragm., n.v).
Melaleuca lancifolia Turcz., Bull. Soc. Imp. Naturalistes Moscou 20:164 (1847).
Melaleuca leucadendron var. lancifolia (Turcz.) F.M.Bailey, Syn. Queensl. f1. 170 (1883).
Typus: Indonesia: SumateraCuming 2427 (KW, holo, n.v.; CGE, FI, K, P, W, iso, n.v).
3b.
Melaleuca cajuputi subsp. cumingiana (Turcz.) Barlow, in Craven & Barlow, Novon
7:113 (1997). Melaleuca cumingiana Turcz., Bull. Soc. Imp. Naturalistes Moscou
20:164 (1847). Typus: Malaysia: Malaya, Malacca, Cuming 2272 (KW, holo, n.v.;
BRI, CGE, FI, K, L, LE, MEL, MO, P, W, iso, n.v).
Melaleuca commutata Miq., Anal. bot. ind. 14 (1850). Typus: Borneo, Korthals
s.n. (L, holo, n.v.; K, iso, n.v.).
3c.
Melaleuca cajuputi subsp. platyphylla Barlow, in Craven & Barlow, Novon 7:113
(1997). Typus: Papua New Guinea: Western Province: near Bula village, mouth of
Morehead River, 4 Aug. 1967, Pullen 6998 (CANB, holo; A, AD, BISH, BO, BRI, E,
G, K, L, LAE, NSW, P, PNH, SING, TNS, US, iso, n.v).
Notes
Myrtus saligna Burm.f. (Fl. Ind. 116 (1768)) was included in the synonymy of
M.cajuputi by Blake (1968) but its type (Indonesia: Java, 1760, leg. ign. s.n. (G, holo,
n.v.)) needs to be examined before the name can be assigned to one of the above
subspecies.
Melaleuca eriorhachis Gand. (Bull. Soc. Bot. France 65:26 (1918)) also was
referred to M.cajuputi by Blake (1968). Its type (Singapore, Ridley (?) s.n. (LY, holo,
n.v.)) similarly needs to be studied before confident placement to subspecies is possible.
4.
Melaleuca clarksonii Barlow, in Craven & Barlow, Novon 7:114 (1997). Typus:
Queensland: Cape York Peninsula, 11.1km SSE of Emu Lagoon, Alice River National
Park, 7 May 1992, Clarkson and Neldner 9582 (CANB, holo; BRI, DNA, K, L, MBA,
MEL, NSW, PERTH, iso).
5.
Melaleuca cornucopiae Byrnes, Austrobaileya 2:74 (1984). Typus: Northern Territory:
Koongarra, 16 Nov. 1975, Dunlop 4030 (BRI, holo, n.v.; DNA, iso, n.v.).
6.
Melaleuca dealbata S.T.Blake, Contr. Queensland Herb. 1:41, figs. 5, 14E, 15E, 15N.
(1968). Typus: Northern Territory: c. Lat. 12 40 S, Long. 131 25 E, Blake 17000
(BRI, holo, n.v.; CANB, iso).
7.
Melaleuca fluviatilis Barlow, in Craven & Barlow, Novon 7:116 (1997). Typus:
Queensland: sandy river bed, Bruce Highway, c. 50km NW of Townsville, 13 Jul.
1985, Barlow and Thiele 3940 (CANB, holo).
Melaleuca nervosa f. pendulina Byrnes, Austrobaileya 2:74 (1984). Typus:
Queensland: Coen River, Brass 19778 (BRI, holo, n.v.; A, n.v., CANB, iso).
8.
Melaleuca lasiandra F.Muell., Fragm. 3:115 (1862). Myrtoleucodendron lasiandrum
(F.Muell.) Kuntze, Revis. gen. pl. 241 (1891). Syntypi: Northern Territory: Fitzmaurice
River, Oct. 1855, Mueller s.n.; Victoria River, Jan.—May 1856, Mueller s.n. (both
MEL, n.v.).
Melaleuca loguei W.Fitzg., J.Proc. Roy. Soc. Western Australia 3:188 (1918). Typus:
Western Australia: S of the Fitzroy River, Logue in Fitzgerald s.n. (NSW, holo, n.v.).
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