Solenostoma Mitt.
Solenostoma Mitt., J. Linn. Soc., Bot. 8: 51. 1865, nom. cons.
Lectotype (Amakawa, 1960): Solenostoma tersum (Nees) Mitt. (≡Jungermannia tersa Nees)
Plants mostly erect or ascending (at least with crowding), deep green but, in sun, locally brownish purple to vinaceous to reddish (at least at ventral leaf bases), usually medium-sized and 550–1500 µm wide or more. Branching usually limited to older regions, the branches virtually always intercalary, from lateral leaf axils, often displaced to, or near to, ventral end of leaf insertion, the branches ascending, soon becoming normally leaved, or geotropic, rhizoidous and leafless; Frullania -type branches present in a few taxa, rare. Stems with cortex often ± distinct, 1(2)-layered, of weakly firm-walled cells, or sometimes of thinner-walled cells forming a hyaloderm; medullary cells thin-walled, infrequently firm-walled, more elongated than the cortical, lacking mycorrhizal infection. Leaves laterally ± spreading, alternate, the insertion usually succubous, but the dorsal end sometimes subtransverse, the lines of insertion extending to stem midline dorsally; leaves unlobed, edentate, ovate to orbicular, the dorsal base usually ± decurrent. Cells thin-walled, with trigones usually distinct, small to somewhat nodose, the cells medium-sized; surface smooth or with distinct, rounded to elliptical to welt-like papillae. Oil-bodies several per cell, granular to very finely papillose, rather large. Underleaves wholly lacking, even in and near gynoecia. Asexual reproduction absent.
Dioecious or paroecious. Androecia intercalary with age, the bracts typically in several to many pairs, similar to leaves but more concave, at least toward the base, unlobed; antheridia usually (1)2–3 per bract, the stalk biseriate. Gynoecia nearly uniformly with a vestigial, low or high ring-like or tubular Isotachis -type perigynium lying in the axis of the stem, at least 1 bract inserted on the perigynium; bracts variable, their shape reflecting that of leaves; bracteole completely lacking. Perianth varying from long-emergent to abbreviated and included within the bracts, cylindrical to clavate, plicate (often 4-plicate) at least distally, the dorsal face of perianth not longitudinally sulcate, the perianth narrowed to mouth, with a beak absent, or if present, then the rostellum never depressed and situated at the truncate apex of the perianth; perianth mouth often crenulate by cells that are free for varying distances at their distal ends, the mouth cells often somewhat elongate.
Capsule subglobose to short-ellipsoidal, often irregularly splitting into 5–6 valves, wall 2- varying to 3- or 4(locally 5)-stratose; outer layer of cells with prominent nodular thickenings; inner layer of cells with semiannular bands, the bands usually complete.
Spores with low, delicate, fine papillae and short-vermiculate markings. Elaters tortuous, bispiral, the ends often thick-walled and nonspiral for varying lengths, the spirals only occasionally extending to elater tips.
Key to Solenostoma in New Zealand
Schuster (2002a, p. 373) stated that Solenostoma “differs from Jungermannia s. str. in several not absolute ways: (a) Solenostoma species almost all develop a low, ring-like to distinctly tubular Isotachis -type perigynium subsequent to fertilization of the gynoecium (at least one ♀ bract is inserted on this); Jungermannia has only a simple, long-emergent perianth; bracts are inserted below the perianth base. (b) Solenostoma almost always develops reddish or vinaceous pigments, at least at ventral leaf bases, usually even in the shade; Jungermannia develops only brown to fuscous pigments. (c) Solenostoma species almost all show only lateral-intercalary branching [a few develop, rarely, isolated Frullania -type branches]; in Jungermannia terminal, Frullania -type branching is usually commonly developed.” Also, “ Jungermannia s. str. is chiefly a Laurasian genus, with almost all taxa in boreal to Arctic regions. By contrast, Solenostoma is virtually cosmopolitan in range...”
We are following, for several reasons, Schuster (2002a) in the recognition of Solenostoma as distinct from Jungermannia. Jungermannia in the broad sense is a “monster genus” (Schuster, 2002a, p. 373), and reduction of the size and circumscription of this and other very large genera makes them less unwieldy and generic limits easier to test. The segregate, smaller units are far easier to deal with in the way of testing differentiating taxonomic characters and assessment of phytogeographical patterns and ecological parameters. The two genera should be subjected to molecular studies prior to a conclusion that they should be treated as congeneric.
Southern temperate species are Solenostoma crassulum (Nees & Mont.) Steph. of Tristan da Cunha, Inaccessible Island, Gough Island, Falkland Islands, southern South America and Juan Fernandez, and six species from our area. These seven species belong to subg. Solenostoma. Two species of subg. Plectocolea Mitt. occur in Chile, S. callithrix (Lindenb. & Gottsche) Steph., which also occurs in Ecuador, Venezuela north to Mexico and the Antilles, and S. decolor (Schiffn.) R.M.Schust., a species also found in Brazil, Ecuador and Venezuela.
According to Schuster (2002a), Jungermannia L. s. str. has seven to eight species, which are, with minor exceptions, all northern. Exceptions are J. ovato-trigona (Steph.) Grolle, which occurs in the Andes, and the Holarctic J. pumila With., which also is known from Tanzania, Lesotho and Natal.
References: Schuster (2002a); Váňa (1975).
