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Formal Description
Agropyron × wallii hybr. nov.
Planta inter A. enysii T. Kirk et A. scabrum (R. Br.) Beauv. Gramen perenne, laxum, glaucum, stoloniferum. Culmi circa 1 m longi, ascendentes vel nutantes, fistulati. Laminae ad 2 mm latae, villosae; vaginae inferiores villosae, superiores glabrae. Ligulae breves, truncatae; auriculae villosae, culmos innovationesque amplectentes. Spicae (3)–5–(7) spiculis, (50)–85–(120) mm longae. Spiculae (2)–5–(7) floribus, appressae, cum aristis 25–40 mm longae, internodis longiores. Glumae subaequales aristiferae, 3–5–nerves. Lemma lanceolatum, dorso rotundatum, apice carinatum et scabrum, basi transverse sulcatum, (7.5)–10–(11.5) mm longum, apice integrum vel 1–2–dentibus lateralibus, 5-nerve; arista (10)–16–(23) mm longa, scabra, purpurascens sicut lemmatis apex. Palea lemma vix aequans, carinis scabra. Callus barbatus, obtusus, 0.5 mm longus. Rhachilla (1.5)–2.0–(2.5) mm longa, setulosa. Antherae (1.5)–2.2–(3.0) mm longae, luteae vel purpurascentes vel purpureae.
Perennial, stoloniferous. Culms lax, ascending to drooping, leafy, hollow, smooth, glaucous, about 1 m long. Branching intra- and extra-vaginal. Leaves up to 2 mm wide, blue-green, glaucous, villous; sheaths of basal leaves villous of culm leaves glabrous. Ligule short, truncate; collar flat; auricles clasping, villous. Spike of (3)–5–(7) spikelets, (50)–85–(120) mm long. Spikelets of (2)–5–(7) florets, appressed, straight, 25–40 mm long including awns, longer than the internodes. Glumes subequal, awn-tipped, 3–5-nerved, longer glume about ⅔ up the lemmas above. Lemma lanceolate, rounded on back, sharply indented at base, keeled and scabrid at apex (7.5)–10–(11.5) mm long, apex entire or with 1–2 lateral teeth, 5-nerved; awn (10)–16–(23) mm long; apex of lemma and the awn frequently purple. Palea sharply keeled, scabrid on the keels, almost as long as the lemma. Callus bearded, obtuse, 0.5 mm long. Rachilla (1.5)–2 0–(2.5) mm long, finely setulose. Anthers yellow through to purple (1.5)–2.2–(3.0) mm long.
Chromosome Number. 2n = 35 (determined by Dr. J. B. Hair).
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Distribution. Porters Pass, inland Canterbury, 2,700ft to 3,000ft.
Holotype. Porters Pass, Canterbury, 3,000ft, coll. H. E. Connor, 5/1/56, in Herb. Botany Division, No. 91921.
Paratypes. Porters Pass, H. E. C., Herbarium Botany Division Nos. 82737, 82738, 82739, 82740, 91920, 91922, 91923, 91925, 91926, 91927, 91928, 91929, 91930, 91931, 91932.
This plant is named in honour of Arnold Wall, Emeritus Professor of English, Canterbury University College, Christchurch, a well known botanist, and an extensive collector of grasses.
Some of the chief morphological features for A. enysii, A. scabrum, and A. × wallii are listed in Table 1, Group Tawera of A. scabrum (Connor, 1954) is used for comparison as it is one of the parents of the hybrid. It will be seen that A. × walli is, for the greater part, intermediate between the parent species.
Hybrids were found at five separate and distinct localities on the eastern side of the Torlesse Range, all in the vicinity of Porters Pass and always near to plants of A. enysii. A. enysii is found in seepages, damp places and on stream banks, while A. scabrum is found chiefly in dry sites, but also in or near the sites for A. enysii.
| Character | A. enysii | A. × wallii | A scabrum Group Tawera |
|---|---|---|---|
| Habit | Stoloniferous perennial | Stoloniferous perennial | Caespitose perennial |
| Culms | Decumbent to nodding. | Decumbent to nodding | Erect to erect-ascending |
| Leaf colour | Bronze | Blue-green | Blue-green |
| Collar | Flat or lopsided | Flat | Flat |
| Auricles | Small, sometimes clasping, glabrous | Long, clasping, villous | Long, clasping, villous |
| Spikelets/spike | Up to 18, appressed, close | 3–6 appressed, ± distant | 3–6 appressed, distant |
| Florets/spikelet | 2–4 | 2–7 | 5–12 |
| Apex of lemma | 2-toothed | Entire or 1–2-toothed | Entire, very rarely 1-toothed |
| Base of lemma | Indented | Indented | Not indented |
| Callus | Short, blunt, with very short barbs | Long, obtuse, with long barbs | Long, obtuse, with long barbs |
| Lemma length* | 6.0–9.5 mm | 7.5–11.5 mm | 7–12.0 mm |
| Palea length | 6.5–9.0 mm | 7.0–11.5 mm | 7–12.0 mm |
| Awn length* | 1.0–3.5 mm | 10–23 mm | 30–53 mm |
| Rachilla length | 1 −2 mm | 1.5–2.5 mm | 2–3 mm |
| Anther length | 2 −2.5 mm | 1.5–3.0 mm | 3–5 mm |
| Anther colour | Yellow | Yellow-purple | Yellow-purple |
| Chromosome number | 2n = 28 | 2n = 35 | 2n = 42 |
[Footnote] * Lemma length and awn length are difficult to determine accurately as the main nerve of the lemma is continuous with the awn, and there is often no definite point where the lemma ends and the awn begins. In A. enysii the apex of the lemma is 2-toothed and the awn definitely begins at the base of the sinus. When the lemma is entire, as in most florets of A. scabrum and some florets of A. × wallii the convention has been adopted of measuring as awn that which projects above the level of the top of the palea, leaving lemma length equal to palea length.
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The hybrid has not been found out in the open dry areas where A. scabrum is common. To judge from the distribution of the hybrids it is, I think, a reasonable assumption that A. enysii is the female parent in the cross.
The hybrid is stoloniferous and an individual plant once established can form a colony in some cases up to 3 feet in diameter. Such a colony looks like many individual plants, and probably develops into a clone of many members.