FAMILY LAMIACEAE MINT FAMILY
Mostly annual or perennial herbs or shrubs with opposite leaves, when
crushed the foliage usually emitting various, mostly pleasant odors. Stems
usually square. Flowers usually abundant and quite attractive, the sepals
and corollas variously united. Calyx 2-lipped or not. Corollas strongly
2-lipped (labiate, hence the family name), rarely 1-lipped. Stamens 2 or
4, epipetalous. Ovaries superior, deeply 4-lobed, rarely not, the style
mostly arising from the middle of the 4 lobes. Fruit comprised of 4 nutlets,
although some of these not maturing, each with a single seed.
The Lamiaceae is a relatively commonly encountered family, especially in the temperate regions of the world. It is comprised of about 3500 species distributed among some 200 genera, most of these herbaceous, less often shrubs, or rarely trees. Many of the species have been taken into cultivation as ornamentals. Some are highly desirable cooking herbs or flavor producers (e.g. Mentha, widely cultivated as a commercial crop plant).
The Lamiaceae is one of the most readily recognized families of flowering plants, at least by the layman. Indeed, it can be fairly accurately stated that any herb or shrub having square stems, opposite leaves, and emitting a minty smell when crushed is likely to belong to the Lamiaceae. The family was for many years referred to as the Labiateae, in reference to the strongly bilabiate (2-lipped) flowers exhibited by most of its species. Modern workers tend to use the name Lamiaceae, as recommended by the International Code of Botanical Nomenclature since consensus has it that each plant family should be based upon a legitimately established genus, in this case the genus Lamium. There is no genus "Labia", the latter name merely an ancient common name bestowed upon members of the family by numerous early workers.
Many current workers (cf. Cantino 1992, and references therein) believe the Lamiaceae to be closely related to the family Verbenaceae, so much so that elements of the latter have been transferred into the former, although technically, the Verbenaceae can be said to have entire ovaries, usually rounded stems which, when crushed, lack minty smells. Early workers, because of its 4-lobed ovaries, thought the Lamiaceae might be closely related to the family Boraginaceae, but recent DNA studies (Olmstead et al. 1992), suggest that the latter belongs elsewhere.
Heywood (1978) gives a concise, well-illustrated, overview of
the family, and the interested beginner is referred to that text for an
introduction to the family. Most species of this family in Texas are attractive
roadside flowers, such as Monarda and Salvia. Yet others are poorly known
localized endemics. Correll and Johnston (1970) provided a technical treatment
of the family for Texas recognizing some 120 species in 31 genera, some
of these introduced and well established roadside weeds.
Cantino, P.D. 1992. Evidence for a polyphyletic origin of the Labiateae. Ann. Missouri Bot. Gard. 79: 361-379.
Cantino, P.D. and R.W. Sanders. 1986. Subfamilial classification of Labiateae. Syst. Bot. 11: 163-185.
Correll, D.S. and M.C. Johnston. 1970. Manual of the vascular plants of Texas. Contr. Texas Res. Foundation 6: 1-1881.
Heywood, V. (ed.) 1978. Flowering plants of the world. Mayflower Books, Inc. New York.
Olmstead, R.G. et al. 1992. Monophyly of the Asteridae and identification of their major lineages inferred from DNA sequences of rbc L. Ann. Missouri Bot. Gard. 79: 249-265.
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