The exact position of the New Zealand plant must remain doubtful until the fructification has been obtained, but it is probably the same as the Australian and Tasmanian Z. tasmanica, which seems hardly different from narrow-leaved forms of the northern Z. marina.
Order LXXXIX. CENTROLEPIDEÆ.
Annual or perennial tufted often moss-like plants, of small size. Leaves linear or setaceous, either all radical or densely imbricated on the short stems and branches. Flowers very small, usually hermaphrodite, one or several within 1–3 bracts, forming little heads or spikelets terminating short scapes or peduncles. Braeteoles or glumes under each flower 1–3, hyaline, sometimes wanting. Perianth none. Stamens 1–2; filaments filiform; anthers versatile, 1-celled. Ovary either 1-celled, or with 2–3 collateral cells, or of 2 or more free or irregularly connate carpels superposed in 2 rows; ovules solitary and pendulous in each cell or carpel; styles as many as the cells or carpels; stigmas linear. Fruit small, dry, pericarp membranous, the cells or carpels opening extrorsely by a longitudinal slit. Seed pendulous or laterally affixed; albumen farinaceous; embryo minute.
A small and inconspicuous order, comprising 4 or 5 genera and about 30 species. With the exception of the New Zealand species, one found in China, and one in antarctic South America, the order is confined to Australia. It has no properties of importance.
| Flowers crowded in a terminal head surrounded by several bracts. Stamens and 1-celled ovaries irregularly mixed, without inner bracts | 1. Trithuria. |
| Flowers within 2 alternate bracts, 1–5 within each bract. Stamen 1. Ovary of 3 or more carpels superposed in 2 rows (rarely reduced to 1) | 2. Centrolepis. |
| Flowers with 2–3 alternate bracts, 1–2 within each bract. Stamens 2. Ovary of 2 collateral cells or carpels | 3. Gaimardia. |
1. TRITHURIA, Hook. f.
Minute tufted and stemless annual herbs. Leaves all radical, filiform. Scapes short, slender, terminatmg in several spreading bracts enclosing a head of minute flowers. Flowers numerous, densely crowded, each probably consisting of a single stamen and ovary, but the stamens and ovaries so closely placed as to appear irregularly mixed. Perianth wanting. Stamens with a filiform filament and oblong anther. Carpels 3-angled or compressed in the Australian species, not angled in the one found in New Zealand. Styles 2–3 or numerous. Fruiting carpels 2–3-angled in the Australian species, splitting from the base upwards into as many valves as angles.
The genus also includes 2 species found in Australia.
