Flora of New Zealand Series

; Lectotype: WELT 68389! T. K[irk] Waihi Lake, Waikato (here designated).

Weak tufts, (7)-20-40 cm, stoloniferous, with decumbent culms rooting at lower nodes, erect or floating above; branching extravaginal. Leaf-sheath chartaceous, smooth, or scabrid, especially towards ligule, uppermost sheaths often scabrid throughout. Ligule 1.5-4.5-(5) mm, long-tapered, acute, entire, becoming lacerate, abaxially smooth or sparsely, minutely scabrid. Leaf-blade 5.5-12.5 cm × (0.6)-1-3 mm, flat, or inrolled, papillose-scabrid, abaxially shallowly ribbed, adaxially more obviously ribbed; margins minutely scabrid, tip acute. Culm internodes smooth, sometimes scabrid just below nodes. Panicle 6.5-13 cm, ± erect, enclosed below by uppermost leaf-sheath; branches and pedicels filiform, scabrid. Spikelets 15-25 mm, 3-6-flowered, pale green; florets chasmogamous and cleistogamous within the same spikelet. Glumes unequal, glabrous, obtuse, margins ciliate-scabrid; lower 2-3.3 mm, 1-nerved, narrow-lanceolate, upper (2.2)-3.5-4 mm, 3-nerved, ± ovate-lanceolate. Lemma (4)-4.5-5.5 mm, 7-nerved, firm, green central portion sparsely scabrid, smooth near base, hyaline margin very wide, finely minutely hairy or scabrid; lemma lobes 2, obtuse; awn 7.5-18 mm, stout, straight, arising from near midpoint of lemma. Palea < lemma, keels densely stiff-ciliate, interkeel glabrous. Callus with ring of fine hairs < 1 mm. Rachilla prolongation 1.5-1.8 mm, hairy above. Anthers in chasmogamous florets 1.4-1.7 mm; in cleistogamous florets 0.4-0.5-(0.8) mm. Caryopsis 1.5-2 × 0.5-0.7 mm.

N.: Rare and scattered, recently collected only in Kaweka Range and Kaimanawa Mts, and at Paekakariki and L. Wairarapa; S.: Westland (Mahers Swamp) and Canterbury (L. Tekapo). Lowland to montane in moderately fertile wetland.

Indigenous.

REPRODUCTIVE BIOLOGY

Flowering in Amphibromus may be chasmogamous or cleistogamous. The cleistogamous florets, which have shorter anthers, may be mixed with chasmogamous florets in the same spikelet, or the plant may bear reduced entirely cleistogamous inflorescences which remain enclosed within the leaf-sheaths.

Also indigenous to Australia; southern New South Wales, Victoria and Tasmania.

Though A. fluitans was earlier recorded from the Waikato and in Taranaki, no recent collections have been made from these areas. Ogle, C. Wellington Bot. Soc. Bull. 43: 29-32 (1987), discussed the future of the sp. in N.Z. and considered it threatened because the type of wetlands in which it occurs have either been lost to intensive pastoral farming or overrun by introduced grasses and other plants. Jacobs and Lapinpuro (1986 op. cit. p. 729) state that A. fluitans is now apparently uncommon in Australia.

LECTOTYPIFICATION

Of 3 specimens at WELT collected by Kirk at Lake Waihi, WELT 68389 was designated lectotype because the florets still remained on the panicle; the other two specimens were overmature.