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Tuatara: Volume 14, Issue 3, December 1966

Note on the occurrence of Thismia Rodwayi F. Muell. at Taurewa, North Island, New Zealand

page 130

Note on the occurrence of Thismia Rodwayi F. Muell. at Taurewa, North Island, New Zealand

Thismia rodwayi F. Muell., a member of the Burmanniaceae, is a small, colourless, usually subterranean saprophyte. Cheeseman (1925) lists it as found in ‘forests at Opepe, near Lake Taupo, on mounds of humus at the base of Podocarpus dacrydioides and other trees’. It has also been recorded from the Tongariro National Park (Druce, 1959), and Trounson Park, North Auckland (W. D. Burke, pers. comm.).

Flowering material and immature capsules were recently (Feb. 1966) found in humus near the base of a large Podocarpus spicatus at Taurewa, 10 miles north of Mt. Ruapehu.

The plants collected consist of sparingly branched rhizomes 5-6 cm. long. The flowers are pinkish-orange, 1-1.5 cm. long, above 2-6 small bracts. Cheeseman describes the flower as ‘perianth campanulate-lanterniform, tube obovate-elongate, distinctly 6-12 costate; outer perianth segments smaller, free, linear or oblong, at first erect but ultimately spreading, sometimes abruptly recurved: Inner segments almost twice length of the outer, linear-spathulate to obovate-oblong, connate or connivent at the tips’. He was unable to find any fruit. The material collected at Taurewa has immature fruit, and shows a marked elongation of the pedicel. (see photograph).

The connate nature of the inner perianth segments is a feature which has caused some confusion in nomenclature as it was formerly accepted as a generic criterion. Thus Cheeseman (1925) placed the New Zealand species in Bagnisia on the basis of this character, but Jonker (1938) found that fusion or otherwise of the segments was too variable to be used in defining a genus. He accordingly widened the scope of the genus Thismia to include species with fused as well as unfused inner perianth segments.

The cortical cells of the rhizome contain an endotrophic mycorrhiza which is suggested by McLennan (1958) to be truly symbiotic rather than parasitic, since globules of fatty material (stainable with osmic acid) are present in the fungal filament. These are set free by rupture of the sporangioles, accumulate in the plant cells and then disappear as metabolism proceeds.

page 131
Fig. 1: Photographs from preserved material of Thismia rodwayi. Above: rhizome, flower and immature fruit with elongated pedicel, × 3. Below: Flower × 5. Photographs by G. K. Rickards.

Fig. 1: Photographs from preserved material of Thismia rodwayi. Above: rhizome, flower and immature fruit with elongated pedicel, × 3. Below: Flower × 5.
Photographs by G. K. Rickards.

page 132

The species is probably more common than the records suggest, as owing to its habitat and rather colourless appearance, it must often have been overlooked by collectors.

References

Cheeseman, T. F., (1908). Notice of the Discovery of a species of Burmanniaceae, a family new to the New Zealand Flora. T.N.Z.I. 41., pp. 140-3.

—— (1914). Illustrations of the New Zealand Flora, Vol. II, Plate 191.

—— (1925). Manual of the New Zealand Flora.

Druce, A. P., (1959). List of the Vascular plants Recorded from Ruapeha, Ngauruhoe, Tongariro and Hauhungatahi.

Jonker, F. P., (1938). A Monograph of the Burmanniaceae. Med. Bot. Mus. en Herb, van de Rijksuniversiteit te Utrecht. No. 51.

McLennan, E. I., 1958. Thismia rodwayi F. Muell and its endoparasite. Aust. J. Bot. 6, 25-37.

Schlechter, R., (1921). Die Thismiae Notiz Zot. Gart. Mus. Berlin-Dahlem 8: 31-45.