Allisoniella E.A.Hodgs.
Allisoniella E.A.Hodgs., Trans. Roy. Soc. New Zealand, Bot. 3: 80. 1965.
Type: P. scottii R.M.Schust.
Type: Allisoniella nigra subsp. novaezelandiae R.M.Schust. (=Allisoniella obcordata E.A.Hodgs.)
Plants rigid, the leafy shoots stiffly ascending to erect, arising from a system of creeping or geotropic, stoloniform axes, the shoots small-leaved below, larger-leaved and denser above, vinaceous to deeply fuscous or piceous (the older sectors often bleached), the shoots relatively vigorous, 410–925 µm wide. Branching copious, the erect leafy shoots not or scarcely branched above, the branches arising from a system of plagiotropic or geotropic, densely rhizoidous, whitish stoloniform branches, the leafy branches occasionally arising from small-leaved basal sectors of erect shoots which originate from plagiotropic axes by suddenly becoming phototropic, the branches usually all ventral-intercalary. Stems with cortex well differentiated, in (1)2–3(4) layers of thick-walled, pigmented cells; medullary cells somewhat to considerably larger, hyaline, thin-walled. Rhizoids on stoloniform axes, lacking on erect leafy shoots. Leaves pectinate-distichous, rather stiffly and widely spreading to subsquarrose, at times rather dense above, transversely oriented, the insertion extending to stem midline dorsally, the leaves often weakly folded or conduplicate, usually bifid to 0.5–0.9; lobes often shallowly adaxially convex or abaxially sulcate at least near gynoecia, with margins (and often sinus) decurved; lobes 15–28 or more cells broad, mostly sharp, the margins entire or feebly crenulate because of projecting cell walls. Cells thick-walled, without trigones, small, the median cells 9–14 × 10–18 µm; surface usually papillose, at times strongly so. Oil-bodies (Schuster, 2002a) 2–4 per cell, rather large, finely granular or finely papillose. Underleaves completely lacking in vegetative sectors. Gemmae rarely developed, colorless or vinaceous, smooth, ellipsoidal, 8.5–10.5 × 14–17 µm.
Autoecious (except probably Allisoniella nigra). Androecia on long leafy shoots, mostly becoming intercalary, compactly spicate; bracts leaf-like but denser, the base concave; antheridia usually single per bract, the stalk 6 cells long, uniseriate. Gynoecia on leading shoots or elongated, often leading, ventral-intercalary branches, the innermost bracts in 2–3 gradually larger series, deeply bifid, like leaves but larger and with margins crenulate-denticulate to denticulate, the lobes usually clearly abaxially sulcate, blunt to sharp; bracteole unlobed or bilobed, connate on both sides with bracts by at least 0.25 to form a distinct sheath around perianth base. Perianth often purplish, long-exserted, deeply and longly 4–5-plicate, the plicae compressed and rib-like and extending nearly to perianth base, the mouth bleached, shallowly and irregularly lobulate, crenulate to feebly denticulate by cells that are weakly to moderately elongated, thick-walled and varying from free only at the tips to completely free.
Seta with 8 rows of outer cells and (3)4–14 rows of internal cells. Capsule ellipsoidal, the wall 2(?) to 3–4-stratose; outer and innermost layers both with small, sharply defined, well-spaced, nodular thickenings, those of the inner layer rarely with short tangential extensions.
Spores 7–11.5 µm in diam., weakly verrucose-papillose or nearly smooth. Elaters 7–9 µm in diam., bispiral.
Key to Species
A genus of five species, four Australasian and one, Allisoniella subbipartita (C.Massal.) R.M.Schust. & J.J.Engel, from southern South America. Of the Australasian species, three occur in our area and one, A. tasmanica R.M.Schust., is endemic to Tasmania. The genus was described by Hodgson (1965) but was placed into synonymy under Cephaloziella by Grolle (1966d); Schuster (1972a) resurrected the genus and distinguished it from Cephaloziella on the basis of several criteria: a) Allisoniella has a seta with 8 rows of outer cells and 4–12 internal cells vs. a seta of the 4+4 type in Cephaloziella; b) the stem in Allisoniella is more rigid, with a well-defined 2–3-stratose cortex, vs. a defined cortex is lacking in Cephaloziella; c) plant architecture differs: Allisoniella normally has leafy axes arising from a system of ramified, microphyllous, plagiotropic or geotropic axes to which rhizoids are almost wholly confined, whereas Cephaloziella exhibits no such shoot dimorphism, and bears scattered rhizoids on normal leafy axes; and d) the capsule wall is 3–4-layered in Allisoniella vs. uniformly 2-stratose in Cephaloziella.
The stiffly ascending leafy axes in Allisoniella tend to be small-leaved below, larger-leaved above, and have an aspect close to that of Marsupella sparsifolia, also found in New Zealand. In the absence of fertile structures, M. sparsifolia differs from Allisoniella by the presence of lateral-intercalary branching and leaf cells with conspicuous trigones.
Description considerably modified from Schuster (1972a).
References: Schuster (1972a, 1996a, 2002a).
