Gackstroemia alpina R.M.Schust.

Engel, John J., 2013, Austral Hepaticae 50. Gackstroemia in New Zealand, together with an interesting new species, Phytotaxa 118 (1), pp. 9-21 : 19-20

Gackstroemia alpina R.M.Schust.

Gackstroemia alpina R.M.Schust., J. Hattori Bot. Lab. 36: 349. 1973 [1972]. Type:— NEW ZEALAND. Stewart Is., Tin Range, Schuster 63-1976 .

Plants closely creeping (like Lepidolaena clavigera ), tinged with magenta to more deeply deep red pigmented or piceous, small in size, 6–11 mm wide (widest point of opposing primary branch tips). Branching regularly 1(locally 2-) to 2-pinnate, the primary branches stiffly spreading, always flat and not twisted toward base of main axis, if 3º branches present, then exceptional and sporadic; ultimate branches (which may at times be the primary branch) with first branch underleaf bilobed, the lobes uniformly galeate. Stems rigid, the cortex of main axes in 1–2 layers of strongly thick-walled, bast-fiber like, pigmented cells; medulla of slightly firm walled, pigmented cells. Rhizoids occasionally developed, on main shoot and primary branches, from stem at immediate base of underleaves. Leaves of main shoot with dorsal lobes imbricate, somewhat elevated above stem, weakly convex and with leaf tips plane or decurved, asymmetrically ovate to subreniform, the apex typically narrowly to broadly rounded, exceptionally with an abrupt short apiculus terminating in a single cell or a hyaline uniseriate row of 2 cells, the tip cell feebly to at most moderately elongate and tapering to a sharp summit, the tooth at times reduced to an angular crenate projection; dorsal margin (= margin nearest stem) plane and not reflexed, entire or with up to 4 teeth, the teeth comprised of a single cell or a uniseriate row of 2 cells, the cells of cilia (esp. the terminal cell) thick walled, the dorsal margin narrowed to the base grading to a weakly cordate base, not auriculate; ventral margin entire or with 1(3) short cilia. Ventral lobe deeply and asymmetrically divided into a typically saccate lobule and a stylus. Lobule (on leaves of main shoot) normally saccate, in some populations exceptional and sporadic ones explanate, then narrowly elongate and with reflexed margins delimiting a rather broad slit, the lobule summit with a tooth (which may consist of a stubby unicellular process or of 2 short cells) or a short to long awn. Stylus cucullate, the margins distinctly reflexed, the stylus broadly elliptic to suborbicular to small and lamelliform or altogether lacking, entire or (often) with a cilium at apex, the margins exceptionally with to 6 cilia. Leaves of primary branches (when 2º branches present) smaller, simpler, lacking a third lobe (stylus), the margins dentate-short ciliate, the armature hyaline, comprised of elongate cells. Leaves of ultimate branches (= 2º secondary branches, or, when these are lacking, = the 1º branches) smaller than those of primary branches and with dorsal lobes more regularly armed with cilia, the cilia with a uniseriate row of -3 elongated cells; lobules of ultimate branches saccate, narrowly elongate-clavate, with a lateral slit, the lobule summit with an elongate awn of 3–4 elongate, thick-walled cells or merely with a unicellular, sharp tooth. Cells with trigones bulging and knotlike, not confluent, the intervening walls between trigones thin, the lumina boundary irregularly sinuate (the uneven line defined by the alternation of bulging trigones and intervening thin walled areas), the median cells 22–29 µm wide × 24–35 µm long; surface smooth. Oil-bodies often found around perimeter of cell, hyaline, (7)9–11 per median leaf cell, homogenous, smooth, elliptic to “peanut shaped.” Underleaves of main stems rigid, brittle, approximate to weakly imbricate, oblate, in small phases sporadically with 1 or both lobes saccate, the underleaves bilobed to ca. 0.2– 0.4, the lobes never transformed into water sacs, typically reflexed and canaliculate-cucullate, terminating in a single cell or a uniseriate row of 2–4 slightly to distinctly elongated cells; lamina with margins narrowly and sharply reflexed to revolute and with the reflexed portion confluent with the recurvature of the lobes, the lamina margins entire or with 1–3 cilia, becoming narrowed and angled to base (ca. 45º to at most 90º), not cordate or auriculate, with tissue adjacent to apex and base of U-shaped insertion line forming an inverted triangle. Underleaves of ultimate branches (which may at times be the primary branch) with lobes uniformly saccate, the water sacs smooth and devoid of armature or with an inconspicuous unicellular projection or a short tooth or a long awn composed of 2–3 elongated, thick-walled cells.

Androecia and gynoecia unknown.

Distribution:— New Zealand: Stewart Is. (5-500 m), South Island (1100-1380 m), North Island (1200– 1280 m).

Comments:—This is the smallest of the New Zealand species of the genus, being less than only 11, to as few as 6, mm wide, and is distinctive by the closely creeping axes (much as in Lepidolaena ). The main stems of G. alpina are typically similar to the branches, in that the lobule is nearly always transformed into a water sac. Unlike G. novae-zelandiae and G. weindorferi , which is not infrequently fertile, G. alpina is known only from sterile gametophytes.

While most populations of G. alpina typically have lobules of main shoot leaves uniformly saccate, a few populations may have sporadic main shoot leaf lobules that are narrowly elongate, with recurved margins to form a strong sulcus. Such populations should be treated with care in distinguishing them from G. weindorferi . See comments under G. weindorferi .