Cephaloziella exiliflora (Gottsche, Lindenb. & Nees) Douin
Jungermannia divaricata var. exiliflora Taylor ex Gottsche, Lindenb. & Nees, Syn. Hepat. 136. 1844.
Jungermannia exiliflora (Taylor ex Gottsche, Lindenb. & Nees) Taylor, London J. Bot. 5: 279. 1846.
Cephalozia exiliflora (Taylor ex Gottsche, Lindenb. & Nees) Trevis., Mem. Reale Ist. Lombardo Sci. Lett. III, 4: 417. 1877.
Type: Australia, Swan River, Drummond 295.
Plants pulvinate and caespitose, typically forming pure, sometimes extensive patches on charred wood, copiously branched in the basal, whitish to bleached, small-leaved (but not microphyllous) shoot system, from which countless erect, usually unramified axes arise, only 4–5 mm high; distal portions of plants rust-red to reddish brown to, occasionally, purplish brown, but perianths bleached at least distally and peripheral parts of ♀ bracts sometimes decolorate. Leafy shoots minute, gradually larger-leaved, the basal decolorate sectors only 150–175 µm wide with leaves, gradually larger above and peripheral to gametangial regions, becoming 350–400 µm wide. Stems lacking pigments, the cortex hyaline, in one layer of weakly defined, moderately thick-walled cells not larger than medullary cells; medullary cells a little thinner walled, variable in size; mycorrhizal infection of cortex or medulla lacking. Leaves laterally spreading to erect-spreading, remote, concave to loosely folded, the mature ones of sterile portions of shoot sectors from 140–150 µm wide × long to 170 µm wide × 150 µm long, when flattened subquadrate to subquadrate-obtrapezoidal, only slightly wider toward apex than medially, bilobed to 0.5–0.6; lobes weakly to moderately divergent, the flanks usually weakly arched; lobes (4)6–7 cells broad usually (near gynoecia to 9–12 cells broad), the apices usually blunt (ending in 1 non-elongated cell or often 2 laterally juxtaposed cells), the lobes usually not incurved; sinus (on flattened leaves) obtuse (sometimes broadly so), with rounded sinus base. Cells firm-walled, variable: in distal, pigmented sectors the primary walls and weak trigones hyaline, only the secondary wall layer adjoining lumen strongly brownish pigmented; in lower shoot sectors all leaf cells hyaline-walled; cells at lobe bases 10–14 µm wide × 13–18 µm long; surface smooth or (?) very obscurely papillose with low, ill-defined papillae locally. Underleaves on weak sterile shoot sectors very small but distinct, on vigorous shoot sectors lamelliform, often broadly triangular to quadrate, 45–55 µm wide × 50–65 µm long, larger toward gynoecia (and there usually bilobed). Gemmae lacking.
Pseudodioecious: ♂ and ♀ gametangia usually terminal on long, leafy axes, the ♀ often abundant and ♂ rare (then seemingly dioecious); connections between ♂ and ♀ gametangia often difficult to demonstrate. Androecia terminal (?always), compactly spicate and rather long, sometimes narrower distally; bracts in 6–10 pairs, closely imbricate, moderately ventricose, bilobed to ca. 0.45–0.55, the lobe margins entire, often blunt to narrowly rounded at the tips; pouched basal sector of bracts formed of relatively large, thinner-walled, elongated cells. Gynoecia terminal, apparently without innovations even in absence of fertilization, initially capitate, strongly pigmented (at most with very tips of bracts and subgynoecial leaves becoming hyaline), the 2–3(4) gyres of rather suddenly much larger and denser leaves concave, superficially mimicking a paroecious inflorescence; bracts of innermost series closely sheathing perianth, bilobed to ca. 0.4, the lobes triangular, mostly irregularly, sparingly denticulate to serrulate, the apex acute and usually ending in a single cell; bracteole connate for 0.35–0.5(0.6) its length with bract on one side or connate on both sides and then forming a conspicuously plicate sheath, the bracteole usually oblong, bifid to ca. 0.4–0.45, the lobes acute, paucidentate. Perianth usually decolorate to greenish throughout (mouth always bleached), 4–5-plicate in upper half, the weakly contracted mouth crenulate with thick-walled, elongated (usually 2.5–3.6:1) cells that are free only at the tips; perianth unistratose at least to near base.
Sporophytes unknown.
Distribution and Ecology : New Zealand and Australia.
“A tiny plant, forming pure and sometimes extensive mats on charred wood, coming in as a pioneer after fires. Cephaloziella exiliflora is one of very few Austral Cephaloziellaceae that forms pure mats, rather than occurring as solitary or somewhat gregarious colonies. It forms almost a ‘lawn’ on burned logs: the countless shoots erect, closely caespitose, and copiously branched below...” (Schuster, 1996a, p. 43).
Comments : Separable from our other taxa of Cephaloziella by the following. 1) The proclivity for formation of pure patches on charred wood. 2) The pale or whitish, translucent older sectors of the caespitose colonies, with only the shoot tips being intensely reddish brown or purplish brown. 3) The tendency for ♀ branches to have blunt leaf lobe tips. 4) Gynoecia, even when not fertilized, do not produce subfloral innovations. 5) Androecia form terminal spikes that do not proliferate vegetatively distally, thus not becoming intercalary. 6) ♂ Bracts have lobe apices blunt to narrowly rounded and margins that are entire. 7) The dorsal margins of leaves on ♀ shoots, and often to a lesser extent ♂ shoots, are oriented edge-on or even weakly reflexed. 8) The leaves of vigorous shoots tend to be slightly folded in the region of the sinus. 9) The irregularly bilobed or often 3–5-lobulate ♀ bracteole apex in gyres of bracts + bracteoles just below the innermost cycle. Such lobulate bracteoles are unknown in other Cephaloziella species (Schuster, 1996a).
Schuster (1972a, 1980b) and Douin (1920) stated that the type of Cephaloziella exiliflora is clearly autoecious to paroecious, and Schuster (1996a, p. 45), after a study of the sexuality of the species, concluded “that some plants are clearly only gynoecial, yet a small minority are demonstrably autoecious.”
Schuster (1996a) commented that the reproductive biology of this species should be studied, and remarked that some populations may be only gynoecial, whereas others may be nearly exclusively so. Schuster (1996a, p. 45) noted that in “some Lejeunea species, there may be 15–30 (or more) gynoecia for every androecium.” It should be emphasized that the physical connection confirming the autoecious condition is often difficult to demonstrate and careful dissection of many plants is normally required.
