Flora of New Zealand Series

A. flaccidum var. shuttleworthianum Hook. f. Handbk N.Z. Fl. 1864, 374.

Rhizome short, ascending; stipites tufted. Stipes stout, up to 15 cm. long. Rhachis stout, smooth, nude, with about 20 alt. to subopp. pinnae. Lamina about ovate-oblong, 20-90 × 5-20 cm., coriac., yellowish green, subacuminate, 3-(4)-pinnate. Primary pinnae up to 10 × 3·5 cm., stalked, ovate-lanceolate, subacute (barren pinnae with broader, less dissected pinnules). Secondary pinnae stalked, c. 3 × 1 cm., about ovate-oblong to lanceolate. Tertiary pinnae c. 1 cm. long, pinnatifid to pinnatisect; segs linear to narrow-oblong, subacute, slightly expanded in region of sori. Sori near tips of segs, solitary, submarginal, oblong, c. 2 mm. long, us. plentiful.

DIST.: K. Sunday Island, rupestral. Also Pitcairn, and Polynesian Islands.

POLYMORPHY

The genus well-, the spp. very ill-defined. Hooker (Fl. N.Z. 2, 1855, 32) remarks "The New Zealand kinds have defied all attempts to be limited by words". We are in but little better position today. There is no doubt that many spp. are plastic, responding markedly to environmental conditions; there is also no doubt that hybridism plays an important part. C. Christensen (Man. Pterid. 1938, 541) says "Many species, even of different groups, hybridize in nature". Cockayne and Allan (Ann. Bot., Lond. 48, 1934) rather too facilely, recognized 15 hybrid groups. There is reasonably good field, but no experimental, evidence for the groups A. bulbiferum × hookerianum (both vars), A. bulbiferum × flaccidum, A. falcatum × lucidum; but the evidence for the other, as for subsequently suggested groups is more slender. No sp. and no hybrid group has as yet been satisfactorily analysed. Reference may be made to the observations of the late Miss Kibblewhite (as cited in Dobbie's N.Z. Ferns 1951, p. 329) who found that "highly characteristic specimens [of A. obtusatum] both from the North and the South Islands, when grown in her fernery for a few seasons, lost their upright habit and fleshiness, and ultimately became quite indistinguishable from A. lucidum". On the other hand specimens of var. obliquum from Breaksea Island, Fiordland, grown in a shaded Wellington garden have shown no visible change in six years. Plants probably of the origin bulbiferum × hookerianum are sts found bearing some fronds of almost pure hookerianum (or colensoi) form, and similar cases are known for bulbiferum × flaccidum. The presence of bulbils on spp. other than bulbiferum is often considered to provide examples of "introgression", but bulbils occ. occur, for example, on forms of A. flaccidum that show no signs of being of hybrid origin. There is a wealth of genetic and cultural work awaiting the student of Asplenium in N.Z.