Flora of New Zealand Series

Spadix sessile, unbranched, permanently enclosed in the sheath of the uppermost If; axis flattened to a thin, membr. strap bearing ∞ fls on its concave outer face; stamens alternating with carpels in 2 longitudinal, often crowded series. Stamen of 2 pollen sacs joined by a curved connective adnate to the axis, each sac simulating a single, ovate, sessile, 1-celled anther. Carpel flask-shaped, rounded at base, attached above the middle by a cushion of tissue. Rhizome ± compressed, creeping, rooting at nodes and there producing either vegetative shoots with short internodes and long lvs or erect, short-lived, sympodial reproductive shoots with longer internodes and us. shorter lvs. Lvs ± translucent; sheath long, open or closed, ± auriculate above; lamina entire, top bluntly truncate or emarginate by erosion; primary nerves parallel, at least 3 (1 median and 2 sub-marginal), sts more; interstitial nerves more delicate, intersected at intervals by ± horizontal cross veins. Plants forming grass-like, mud-collecting swards. Cosmopolitan genus of c. 12 spp. N.Z. representatives are referred to 2 Australian spp., but the descriptions are drawn up from N.Z. plants.

Setchell (Proc. nat. Acad. Sci., Wash. 19, 1933, 810–817) recognizes 3 sections of which only Zosterella is represented in N.Z. Characters distinguishing this section are: Retinacula regularly present opp. all except the ± aborted lowest and uppermost fls; lf-sheaths open; testa ecostate. Low or moderately tall spp. with 3- (often appearing 1-) nerved lvs (except in Z. capricorni); rhizomes with 1 lateral bundle on each flank and fibre strands in inner portion of cortical layer; spathes from slightly to decidedly broader than the peduncular internode. A retinaculum is a ± triangular flap arising outside each stamen and just within the elevated margin of the infl.-axis.

Fig. 1. ZOSTERA. Z. muelleri : inflorescence, front and side views, stigmas exserted, spadix enclosed in spathe; fruit; seed; leaf-venation. Z. capricorni : leaf-venation; spadix bent outwards from spathe and showing young fruits and between them a hook-shaped scar left by the connective of each stamen. © All rights reserved. [Image: 4X20]