Solitary graminoid forb growing in dense or loose tussocks with all branching inside leaf sheaths (intravaginal). Tussocks 5–15 cm in diameter or more diffuse and much larger in moss carpets. Base of shoots with a firm sheath of whitish, withered leaves. Aerial shoots with several, hyaline prophylls. Culms 4–12 cm, erect, smooth and glabrous.
Leaves with keel, flat or folded, smooth and glabrous. Basal leaves 2–5(10) cm long, shorter than culms, 0.8–1.2 mm broad, tapering in the distal part. Culm leaves 1–2, similar to basal leaves but shorter, 1–3 cm; flag leaf blade 1–2.5 cm, attached below middle of culm. Ligula 0.8–2.3 mm, acute.
The units of the inflorescence of Poaceae are the spikelets, nearly always numerous in a panicle or spike-like inflorescence. Spikelets are composed of 2 glumes (bracts for the spikelet) and one or more flowers (the term used below) or rather floral units often named ‘florets’ because we do not know what is the exact flower. A flower or floret is composed of a lemma with 1 mid vein (probably the floral bract), a palea with 2 mid veins (either 2 fused bracteoles or perhaps 2 fused perianth leaves), 3 small organs called ‘lodiculae’ and essential in the opening of the flower at anthesis (possibly transformed perianth leaves or transformed stamens).
Inflorescence an open or dense panicle (1.5)2–3.5(4) cm long, occupying 1/3–1/2 of culm length, ovoid in outline, usually strongly tinged with purple. Panicle with 5–7 nodes, with 5–8(9) branches at each of the lower nodes. Branches 8–25 mm, ascending or rarely spreading, smooth, each with several spikelets (6–8 on the longer branches). Spikelets 1.5–2.3 × 0.5–0.8 mm, more than 2 times as long as broad, with (1)2(4) flowers, usually 2 developed and above these sometimes 1–2 rudimentary flowers. Bracts (glumes and lemmas) with rounded backs. Glumes small, obtuse, often fringed (erose), with indistinct mid vein, with a dark purple mid section and a broad golden yellow hyaline margin to the apex. Lower glume 0.3–0.6 mm; upper glume 0.8–1.1 mm, up to 1/2 as long as spikelet, persistent. Lemmas 1.5–2 × 0.4–0.6 mm, narrowly ovate or obovate, truncate or acute, often fringed (erose), with (1)3 veins, densely pubescent with short, stiff hairs on and between veins up to ca. 1/2 its length, veins and mid section of the lemma deep purple to the apex with a broad golden yellow hyaline margin. Paleas slightly shorter than lemmas, 1.2–2.0 mm, with spinulose keels. Stamens 2–3; anthers ca. 0.7 mm but shrivelled (non-functional).
Fruit not developed.
No seed reproduction recorded anywhere; anthers and fruits abort at an early stage of development. Restricted and local vegetative reproduction by fragmentation of tussocks, seen in the very loose tussocks found in deep, wet moss carpets (in the Sassen area; R. Elven & N.W. Steen observ.).
Pucciphippsia vacillans can only be mistaken for one of the two species of Phippsia: P. concinna. It differs most distinctly from Phippsia in having usually 2 flowers, persistent glumes with an indistinct mid vein, lemmas with a golden yellow hyaline margin (white in the Phippsias), and always aborting anthers. Less distinct differences are found in the leaves, more narrow and not with as distinct boat bow apex as in Phippsia, longer culm leaves and ligulas, and especially in a strange panicle with predominantly ascending branches, not erect as in Phippsia algida and not spreading or retrorse as in well-developed plants of P. concinna. It shares its deep purple coloration with P. concinna.
On open or more often moss-covered, fine-grained or gravelly ground, usually along shores of brooks and lakes, in seepages, and in other permanently or frequently wet places, sometimes in deep, moist or wet moss carpets where it may be non-flowering (and difficult to find and identify). Mainly found in areas with substrates with a circumneutral or basic soil reaction (pH).
Cryophilous. Pucciphippsia vacillans is known from localities scattered in all zones and sections on Spitsbergen, Nordaustlandet, Barentsøya and Edgeøya. It is locally frequent in the inner and middle parts of the Isfjorden and Wijdefjorden districts, but also rather frequent in NW and N Nordaustlandet (Gustav Adolf Land, Gustav V Land, Prins Oscar Land), in some of the harshest parts of Svalbard. It has not been recorded from Bjørnøya.
Until the 1960s, Pucciphippsia vacillans was considered restricted to Svalbard and Novaya Zemlya. Hedberg (1962) then reported it from the Canadian Arctic Archipelago (and as triploid with 2n = 21). It has since been found in several places in Canada and one place in Greenland (Darbyshire 2007).
Pucciphippsia vacillans is a mystery plant, in spite of several studies addressing it. Scholander (1934) found it enigmatic and treated it in an eight page description and discussion in connection with the flora of NE Svalbard. It was assigned to Puccinellia (e.g., Scholander 1934) or Colpodium (e.g., Rønning 1963) until Hedberg (1962) found it to be a triploid hybrid (2n = 21; based on Canadian plants, a number later confirmed by Steen 2000 and Steen et al. 2004 on plants from Svalbard) with one parent diploid (Puccinellia vahliana) and one tetraploid (one of the two species of Phippsia). The nomenclatural consequence was drawn by Tzvelev (1971) when describing the new hybrid genus Pucciphippsia.
Pucciphippsia vacillans has been accepted as a hybrid species from Puccinellia vahliana and Phippsia algida since Hedberg (1962) proposed that origin, in spite of its general appearance being more in correspondence with Phippsia concinna. Hedberg's opinion was based on plants from Canada where Phippsia algida was the only species of the genus accepted at that time. Later studies have shown that also P. concinna is widespread in arctic Canada, and the question of parentage needed to be re-opened. The investigations of Steen (2000) and Steen et al. (2004), based on isozymes, morphology and cytology, showed by a rather elegant morphological analysis that the Phippsia parent is P. algida (in spite of the general similarity between Pucciphippsia vacillans and Phippsia concinna). She got little help from the isozyme data. Among the six enzymes studied, Pucciphippsia vacillans showed an additive pattern in one (6-PGD), the only one where Puccinellia vahliana had a band not present in both species of Phippsia. In all other enzymes studied, Pucciphippsia vacillans was identical to both species of Phippsia, whereas Puccinellia vahliana had a more simple multilocus phenotype than Phippsia for five out of six enzymes but with the same bands.
The mystery is how Pucciphippsia vacillans behaves in the field. It has never been observed with a developed anther with pollen or a developed fruit. All studies show that it is sterile, not unexpected from its triploid chromosome number. It has intravaginal branching only, with no means of vegetative reproduction except for very local fragmentation. In spite of this, it usually forms populations with numerous separate individuals, often over rather large areas (both in Svalbard and Canada). Steen (2000) and Steen et al. (2004) discussed this problem but did not propose any explanation. Some fragmentation may take place when it grows in deep, wet moss carpets but not when it grows on more open ground, as it very often does.
Darbyshire, S.J. 2007. ×Pucciphippsia Tzvelev. – In: Flora of North America Editorial Committee (eds.), Flora of North America north of Mexico. 24. Magnoliophyta: Commelinidae (in part): Poaceae, part 1: 477–478.
Hedberg, O. 1962. The genesis of Puccinellia vacillans. – Botanisk Tidsskrift 58: 157–168.
Rønning, O.I. 1963. The Spitzbergen species of Colpodium Trin., Pleuropogon R. Br., and Puccinellia Parl. – Kongelige Norske Videnskabers Selskab Skrifter 1961-4. 50 pp.
Scholander, P.F. 1934. Vascular plants from northern Svalbard with remarks on the vegetation in North-East Land. – Skrifter om Svalbard og Ishavet 62. 155 pp.
Steen, N.W. 2000. A test of the hybrid origin hypotheses of Pucciphippsia vacillans (Poaceae) in Svalbard, by use of enzymatic, morphological and cytological data. – Cand. scient. thesis, Univ. Oslo, Oslo.
Steen, N.W., Elven, R. & Nordal, I. 2004. Hybrid origin of the arctic X Pucciphippsia vacillans (Poaceae): evidence from Svalbard plants. – Plant Systematics and Evolution 245: 215–238.
Tzvelev, N.N. 1971. Zametki o zlakach flory SSSR, 6. – Novosti Sistematiki Vysshykh Rastenii 8: 57–83.