Flora of New Zealand Series

Panax discolor Kirk in T.N.Z.I. 3, 1871, 178.

Shrub up to c. 5 m. tall, much-branched, with 3-5-foliolate lvs and occ. unifoliolate ones. Petioles slender, 2-8 cm. long; lflts subsessile, obovate- to elliptic-cuneate, coarsely and sharply serrate, acute to sub-acuminate, bronze to yellowish green above, paler below, coriac. Terminal lflt 4-8 × 1·5-2.5 cm., on short petiolule. Umbels terminal; staminate with 4-10 rays, 3-8 cm. long, the fls racemosely arranged; pistillate with rays 2-5 cm. long, umbellules irregular, 2-6-fld. Ovary 5-loculed, or locules fewer by abortion, 5-ovuled, style-branches 5, connate at base, tips free. Fr. c. 6·5 mm. long, oblong in outline.

DIST.: N. Shrubland and lowland forest from lat. 35° to 37°.

FL.- FT. 11-2.

HETEROBLASTY AND HYBRIDISM

The situation is no less complicated than in Neopanax. P. edgerleyi has as many juvenile and semi-juvenile forms as N. simplex, and some can hardly be determined other than by the pronounced aromatic odour of the crushed lvs. P. lineare, P. crassifolium, P. ferox and P. chathamicum form a distinct group, characterized by their similar life-histories and narrow, very coriac. lvs. The status of Kirk's var. trifoliolatum of P. crassifolium is still uncertain; some of the 3-5-foliolate forms may be, as suggested by Cockayne and Allan (Ann. Bot., Lond. 48, 1934, 33), due to hybridism with P. lessonii. There is good evidence that the two spp. do hybridize, but whether any of the hybrids are fertile is not known. P. gilliesii is at present too little studied to determine its exact status. Again, there are intermediate forms between P. crassifolium and P. ferox, but breeding tests have not been applied. Cockayne and Allan (T.N.Z.I. 56, 1926, 28) discuss specimens from Kapiti Id suggestive of the origin Neopanax arboreum × Pseudopanax crassifolium, characterized especially by the breadth of the lvs, the spreading not reflexed position, intermediate texture and venation. From specimens transplanted into gardens and from continuous observation on the island it is known that juveniles with lvs of this form develop into round-headed trees, not easily distinguished from P. crassifolium, but producing reversion shoots with the broad lvs characteristic of the juveniles. Such trees flower and fruit; the range of form in seedlings has not been determined, but is known to include some with broad lvs. Similar broad-lvd plants are known also from coastal scrub in Coromandel Peninsula and North Auckland; in lowland forest from about lat. 40° southwards unbranched juveniles with similar broad lvs, resembling those of semi-juvenile P. chathamicum, are not uncommon, and present an aspect, with their spreading lvs, very distinct from that of juveniles of either P. crassifolium or P. ferox.

Reversion shoots of juvenile and semi-juvenile form occur not uncommonly on adult trees, especially of P. crassifolium; adult trees completely defoliated by fire have been observed to become reclad in lvs showing all transitions from completely reflexed juveniles to adults, and to re-flower in this condition.