Essential Oils: Botanical
Modern Botanical Nomenclature.
Alexandrian Laurel Calophyllum inophyllum L.
So, today, plants are classified under the binomial system invented by Carl Linneus (1707-78), a Swedish botanist. In this system, the first name given is that of the genus, and the second, that of the specific epithet e.g. for creeping or Corsican mint Mentha requienii Bentham, the genus is Mentha, of the Labiatae family, M. requienii being one of some 25 species of aromatic herbs contained in this genus. The binomial (‘two stage naming’) system gives a precise classification of the particular plant, and these classifications are to be found Linnaeus’s two definitive original works: Genera plantarum and Species plantarum. Botanists have further developed this system into a comprehensive diversely branched family tree of classifications, which includes all known plants. The complete ascending sequence is species, genus, family, order, class and division.
The meaning of the botanical name may be indicative of the history of the plant i.e. a genus may be named after a particular botanist e.g. the Kaempferia genus of some fifty herbal species withy rhizomes & tuberous roots which includes some lesser gingers, is named after the German physician Englebert Kaempfer 1651-1716. The name may also tell something of the habit or morphological characteristics of the plant e.g. in Gaultheria procumbens L., the latter name derives from ‘procumbent’ which describes the plant’s habit. A useful publication which is the standard reference for botanical latin (& which includes comprehensive listings of the meaning of plant names) is listed below under Stearn (1992).
The Rules of Plant Nomenclature.
Plants are divided into families in which similarly related plants are grouped together basic on the clear similarity of morphological characteristics.
Families may contain one genus or a large number. A genus may similarly contain one species or a large number of related individuals – for example the Rosmarinus genus contains just two species, Rosmarinus eriocalix Jord. & Fourr. and R. officinalis L. (although some workers recognise Rosmarinus tormentosus Huber-Morath & Maire, as a third species of the genus). Variations occur within a species and these are accommodated in the following manner: a subspecies (ssp.) is a distinct variant often arising because of evolution of plant form from geographic factors, varieties (var.) have small differences in morphology, and the form (forma), has very minor differences e.g. leaf or fruit colour. Cultivars offer further evidence of diversity and according to The International Code of Nomenclature for Cultivated Plants (1980), cultivars named since 1959 should be given vernacular names, which should be in roman type within quotes e.g. “Rosa”.
Hybrid plants arising from the sexual crossing of distinct species within the same genera are called interspecific hybrids and are indicated by a multiplication sign e.g. Lavandin plants Lavandula x intermedia are sterile hybrids between Lavandula angustifolia Mill. and Lavandula latifolia Medic. Less commonly met are plants arising from sexual crossings between different genera (intergeneric hybrids). Grafting one plant onto another can also produce hybridised plant growing onwards from the grafting point: these are indicated by a + sign linking the two involved species.
Chemotypes (ct.) are of especial interest in the world of essential oils. These are marked by differences in products of secondary metabolism (e.g. essential oil composition) which can occur even in morphologically stable species, such as Chamomilla recutita (L.) Rauschert. For example, four chemotypes of Ocimum sanctum L. from the highly varied Ocimum genus were described by Hegnauer (1966): a citral-type, a eugenol type, a methyl chavicol type and a chavibetonal type. The distinguishing criteria for chemotype identification are the major components only of the essential oil from a named specific part of the plant (seeds, leaves etc.). Genetic control of essential oil biosynthesis has been investigated and a bank of knowledge now exists for specific oil-bearing plants. It is probable however that many chemotypes of common aromatic plants have yet to be properly identified.
Botanical nomenclature for essential oil definition.
Botanical name plus naming botanist. The botanist’s name is important
because for example, the Arolla pine tree was classifed as Pinus montana
Lamark (syn. Pinus cembra L.) whereas Pinus montana (Miller) is now taken
as syn Pinus mugo Turra – the Mountain Pine.
The INCI system.
ISO standard 4720 (2002).
Example and glossary.
ct. or bs. - chemotype
Hegnauer R. (1966): Chemotaxonomie der Pflanzen Band 4, Birkhäuser Verlag, Basel und Stuttgart, Germany.
Jian-Qin Cu (1996) "Geranium oil from Yunnan, China" Perf. & Flav. 21, p23.
Kokkini S. (1992) “Essential Oils as Taxonomic Markers in Mentha” in R.M. Harley & T. Reynolds (editors) Advances in Labiate Science pp. 325-334 pub. Royal Botanic Gardens, Kew.
Mabberley D.J. (1998) The Plant Book 2nd rev edn. Cambridge Univ. Press.
Soulier D-J. “The Rosmarinus Genus” in Les Cahiers de l’Aromathérapie – Aromatherapy Records No. 2 Sept 1996 pp29-35.
Stearn, William T. (1992) Botanical Latin 4th edn Timber Press, Portland Oregon 1992.