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Volume IV (1988) - Flora of New Zealand Naturalised Pteridophytes, Gymnosperms, Dicotyledons
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Mentha L.

MENTHA L.

Usually perennial, rarely annual, herbs with creeping rhizomes or stolons. Lvs simple, aromatic, usually toothed. Verticels usually dense, many-flowered, axillary or in terminal spikes or heads, or as few as 2 fls per verticel, or rarely fls solitary. Fls ⚥ or ♀. Bracts leaflike or reduced. Calyx tubular or campanulate, 10-15-nerved, not gibbous at base, generally hairy inside; teeth (4)-5, equal or unequal. Corolla tube < calyx; limb 4-lobed, subequal and scarcely 2-lipped; upper lobe wider and usually emarginate. Stamens almost equal, divergent or lying together beneath upper corolla lip, generally exserted. Style gynobasic, its branches subequal. Nutlets ellipsoid to suborbicular or ovoid, smooth, reticulate or tuberculate.

Key

1
Fls in dense terminal spikes or heads composed of 1-few whorls
2
Fls in distant axillary whorls with cluster of lvs at shoot apex, (1)-few to many per whorl
4
2
Lvs usually distinctly petiolate, sometimes subsessile on shoots in water, peppermint- or lemon-scented
3. * × piperita
Lvs sessile or subsessile, not peppermint- or lemon-scented, often spearmint-scented
3
3
Lvs broad-elliptic or ± ovate, rugose, greyish tomentose or densely hairy beneath
6. *suaveolens
Lvs lanceolate to elliptic or ovate, plane or if rugose then green with only scattered hairs below, sometimes grey-tomentose below but then lanceolate or elliptic-lanceolate
5. *spicata
4
Calyx prominently glandular; corolla mauve or purple
5
Calyx eglandular, or if not, then glands ± obscured by hairs; corolla white or pale mauve
6
5
Lamina > 2.5 cm long; calyx glabrous inside
1. *arvensis
Lamina < 2.5 cm long; calyx densely hairy inside
4. *pulegium
6
Plant ± erect; lvs lanceolate, > 2 cm long, verticels many-flowered
2. *australis
Plant prostrate; lvs orbicular or broad-ovate, < 1.5 cm long; verticels 1-3-flowered
7. cunninghamii

c. 25 spp., N. temperate regions, South Africa, Australasia. Native sp. 1, naturalised 5 and 1 cultivated hybrid.

Fls of all the common spp. are shown in Fig. 77 or Plate 15.

Fig. 77. Fls of Mentha. A M. arvensis; B M. × piperita; C M. pulegium; D M. spicata subsp. spicata. © All rights reserved. [Image: 4X64]
Fig. 77. Fls of Mentha. A M. arvensis; B M. × piperita; C M. pulegium; D M. spicata subsp. spicata. © All rights reserved. [Image: 4X64]
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