Microtis

For the mollusc genus, see Microtis (mollusc).

Onion Orchids
Microtis media, Illustration.
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Monocots
Order:	Asparagales
Family:	Orchidaceae
Subfamily:	Orchidoideae
Tribe:	Diureae
Subtribe:	Prasophyllinae
Genus:	Microtis R.Br., 1810
Species
See text.

Microtis (onion orchids) is a small genus in the orchid family Orchidaceae.

Description

These orchids occur from South China to Japan, Australia (except the Northern Territory), New Zealand and the south west Pacific, in grassland and scrub.

They are deciduous, chlorophyllous, sympodial, tuberoid terrestrial orchids with a single, cylindrical leaf that encloses the stem.

The tiny flowers are green and arrange in a many-flowered (50 to 100) spiral in a spike or raceme around the erect and tall central stalk. The lowermost flowers are close the exit of the stalk from the sheating leaf. The dorsal sepal is sharp-pointed and forms a hood over the column. The lateral sepals are oblong and sometimes recurved. The dorsal sepal often keeps the oblong petals out of sight. The lip is ovate-oblong with united basal calli. The lobed lip has a rough, irregular margin.

Every flower tends to set seed, after being pollinated by wingless worker ants from the genus Iridomyrmex, attracted by nectar at the base of the lip. This is an exceptional case of pollination by ants, since ants tend to secrete an antifungal substance that kills pollen. This doesn't seem to affect Microtis pollen.

Microtis orchids are often cryptic and difficult to differentiate. Microtis unifolia seems to have three different groups in New Zealand with different geographical ranges, habitats and flowering times.

Species

• Microtis alba R.Br. (1810) (SW Australia)
• Microtis angusii D.L.Jones (1996) (New South Wales) (endangered)
• Microtis arenaria Lindl. (1840) : Notched Onion Orchid (Victoria, Tasmania)
• Microtis atrata Lindl. (1840) (SW Australia, Tasmania)
• Microtis brownii Rchb.f. (1871) (SW Australia)
• Microtis densiflora (Benth.) M.A.Clem. (1989) (SW Australia)
• Microtis eremaea R.J.Bates (1996) (SW Australia)
• Microtis familiaris R.J.Bates (1990) (SW Australia)
• Microtis globula R.J.Bates (1984) (SW Australia)
• Microtis graniticola R.J.Bates, (1996) (SW Australia)
• Microtis media R.Br. (1810) (SW Australia)
  • Microtis media eremicola R.J.Bates (1996) (SW Australia)
  • Microtis media media (SW Australia)
  • Microtis media quadrata R.J.Bates, (1990) (SW Australia)
• Microtis oblonga R.S.Rogers (1923) (SE Australia)
• Microtis oligantha L.B.Moore, (1968) (New Zealand North Island)
• Microtis orbicularis R.S.Rogers (1907) (S. Australia)
• Microtis parviflora R.Br. (1810) : Slender Onion Orchid (Malesia to SW. Pacific)
• Microtis pulchella R.Br. (1810) (SW Australia)
• Microtis rara R.Br., Prodr. (1810) (Queensland, New South Wales)
• Microtis unifolia (G.Forst.) Rchb.f. (1871) : Common Onion Orchid (S. China to Japan and SW. Pacific) (abundant)

Cultivation

Most Microtis are very easy to grow, and readily volunteer themselves in other pots. Microtis are often found in gardens around Melbourne from wind-born seed.

References

• Jones D.L. (1996). "Microtis angusii, a new species of Orchidaceae from Australia". The Orchadian 12 (1): 10–12. 
• R. Peakall, A. J. Beattie (1989). "Pollination of the Orchid Microtis parviflora R. Br. by Flightless Worker Ants". Functional Ecology (British Ecological Society) 3 (5): 515–522. doi:10.2307/2389565. JSTOR 2389565. 

External links

• New Zealand Native orchid group