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Electronic Flora of South Australia genus Fact Sheet

Family: Labiatae
Prostanthera

Citation: Labill., Nov. Holl. Pl. Sp. 2:18 (1806).

Derivation: Greek prostheke, appendage; antheros, flowery; botanical Latin anthera, anther; alluding to the small appendage of the anthers.

Synonymy: Not Applicable

Common name: Mintbushes.

Description:
Small shrubs, to c. 2 m high; branches and leaves with oil glands which are usually strongly scented when crushed (P. behriana lacks odour); leaves opposite; venation and midrib usually not visible, sometimes faint.

Inflorescence raceme-like on leafy branches; part-inflorescence 1-flowered with accessory buds sometimes present; prophylls (bracteoles) 2, opposite, rarely alternate; calyx 2-lipped to 2-lobed; corolla distinctly 2-lipped, 5-lobed; lower median lobe directed outwards and forward to recurved, usually emarginate; lateral lobes spreading to reflexed; upper median lobe-pair directed outwards and forward, concave in section, often reflexed distally; stamens 4; filaments ligulate to subterete, usually glabrous, white; anthers basifixed between the lobes, 2-locular, introrse; connective often extended to form 1 or 2 basal appendages; ovary cup-shaped to cylindrical, 4-lobed, often glandular distally; style terminal, slender, ligulate to terete, slightly incurved, lying next to upper surface of the corolla; stigma shortly 2-fid.

Fruiting calyx often greatly enlarged; lower lobe inward folded (section Prostanthera) or directed outwards and forward (section Klanderia); mericarps 4, usually reticulate-rugose; seeds slightly flattened, ellipsoid to cylindrical-ellipsoid, slightly incurved, 1-2.5 mm long, 0.2-0.8 mm wide, thickened distally.

Distribution:  About 80 species, endemic to Australia. (B. J. Conn (1984) J. Adelaide Bot. Gard. 6:207-348).

Biology: No text

Key to Species:
1. Corolla with lower median lobe longer than the upper median lobe-pair; corolla white, pale-blue, mauve, purple, sometimes with a tinge of pink; calyx with lower lobe folded inwards over the mericarps, upper lobe significantly longer than the lower lobe [section Prostanthera]
 
2. Branches with spines present
 
3. Calyx lobes very unequal; shrub glabrous except for a few hairs at the distal nodes; branching more or less patent and distant
P. nudula 8.
3. Calyx lobes more or less equal in length; shrub usually hairy; branching more or less erect and relatively crowded
P. spinosa 10.
2. Branches not spiny
 
4. Leaves terete
P. baxteri var. sericea 2.
4. Leaves more or less flat or incurved, not terete
 
5. Upper calyx lobe more or less equal to lower calyx lobe; leaves 1.5-2.5 mm long
P. eurybioides 6.
5. Upper calyx lobe much longer than the lower calyx lobe; leaves at least 4 mm long, rarely as short as 2.8 mm
 
6. Pedicels, bracteoles and calyces glabrous or sparsely hairy; corolla white with purple striations
P. striatiflora 11.
6. Pedicels, bracteoles and calyces moderately to densely hairy; corolla a mauve pale-violet, blue to white, purple striations may be present
 
7. Calyx not enlarged in fruit; leaves sparsely to densely hairy sometimes sparsely hairy adaxially, often glabrous abaxially
P. behriana 3.
7. Calyx enlarged in fruit; leaves sparsely to densely hairy on both surfaces
 
8. Hairs appressed to patent, antrorse to retrorse, hence indumentum appearing scruffy
P. wilkieana 12.
8. Hairs appressed, antrorse, hence indumentum appearing more or less smooth
 
9. Bracteoles 3.8-8.1 mm long, 0.4-1.1 mm wide; branches, leaves and calyces silky
P. sp. A 13.
9. Bracteoles 0.7-3.6 mm long, 0.1-0.4 mm wide; branches silky, leaves and calyces usually not appearing silky
P. sp. B 14.
1. Corolla with lower median lobe more or less equal to upper median lobe-pair; corolla red, orange, yellow, or dark (metallic) blue-green, rarely mauve; calyx with lower lobe remaining more or less directed outwards and forward or recurved, not enclosing the mericarps, lobes more or less equal in length [section Klanderia]
 
10. Hairs irregularly branched, more or less densely covering branches, leaves, pedicels and calyx (simple hairs may also be present) . P. chlorantha 5
 
10. Hairs simple, sometimes with a few branched hairs on the calyx (KI populations of P. serpyllifolia subsp. microphylla), never on branches or leaves
 
11. Hairs of branches, leaves and calyces stiff, straight, appressed and antrorse
P. calycina 4.
11. Hairs of branches, leaves and calyces more or less soft, recurved to reflexed, never appressed, frequently curled
 
12. Leaves ovate to narrowly ovate, sometimes suborbicular
P. serpyllifolia 9.
12. Leaves more or less terete to linear-obovate
 
13. Anther appendage 1-2.5 mm long; calyx 7-12 mm long
P. florifera 7.
13. Anther appendage to 0.3 (rarely to 0.5) mm long; calyx 5-7 mm long
P. aspalathoides 1.

Author: Not yet available


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