Tuatara: Volume 25, Issue 2, January 1982
Notes on Some Anthocerotae of New Zealand (2) — The Genus Anthoceros
Notes on Some Anthocerotae of New Zealand (2)
The Genus Anthoceros
|(ii)||Anthoceros coriaceus Steph.|
References and sources of material.
A. coriaceus was described by Stephani in 1916 from a specimen collected by T. Kirk in New Zealand (Stephani 1912-1917) and now lodged in the Stephani Herbarium at Geneva (T. Kirk 112; G. 19821). This specimen, along with notes made by Stephani, was kindly made available for inspection. Two other specimens which were examined came from the Herbarium of E. A. Hodgson. One of these (H 1623; MPN 17066) was collected by E. A. Hodgson at Kiwi Valley, Wairoa, New Zealand in 1923 and determined by W. E. Nicholson as probably A. coriaceus; the other (H 7622; PRB 17145; MPN 17072) was collected in the Manawatu Gorge, New Zealand by V. D. Zotov in 1936 and determined by E. A. Hodgson as probably A. coriaceus. The account below is based mainly on living plants collected from roadside banks on the south side of Tarata Saddle, Taranaki in November 1979 and kept growing at Massey University. Voucher specimens are lodged in the Herbarium of Massey University (MPN 17073).
Morphology of the gametophyte.
The thallus is perennial, dioecious, firm in texture and of a subglaucous to green colour. It is firmly attached by rhizoids either to the soil or to old thalli which it has overgrown. The thallus may be ligulate and up to 1.5cm long and 7mm broad, but commonly it is repeatedly branched, the broad branches spreading outwards to form a partial rosette up to 2cm broad and 3 (-4)cm long (Figs. 1 and 2). The border is irregularly lobed and finely crenate. Older parts of the thallus gradually die off as the thallus extends. In January at the margin of some thalli there appear plate-like, multicellular gemmae which are readily detached and are dispersed in water. Often they attach by rhizoids to the upper surface of older parts of the thallus. Male plants are usually flat and have a few scattered antheridial cavities, each containing one large antheridium, with a body up to 270 microns wide and 300 microns long and a stalk of 3 (-4) tiers of cells. In female plants the edges of the thallus are often upturned and connivent, so forming a shallow cup, on the floor of which are one or more embedded archegonia and later sporophytes.
Anatomy of the thallus.
In a transverse section of a young thallus the upper epidermis is distinctive, for it is composed of thin-walled papillate cells, but with age it may erode (Fig. 3). Cells of the lower epidermis may have a thickened outer wall and may carry rhizoids. The compact ground tissue in well-developed female thalli is 10-12 (-16) layers deep in the central region and is gradually reduced to some 3-6 layers towards the margin, but in male thalli the central region is only 6-8 layers deep. The interior cells often show pitting on the walls and trigone thickenings at the angles. A single, bright green, disc-shaped chloroplast lies close to page 66
Morphology of the sporophyte.
The capsule is 1-1.5cm tall and 0.4-0.5mm broad; it is surrounded at the base by an involucre 2mm high. When first it opens, the upper part is golden in colour but later it turns brown. There are stomata in the capsule wall. Other epidermal cells mainly have the outer and radial walls conspicuously thickened but on two sides of the capsule there is a longitudinal line, two cells wide, of thin-walled cells. Dehiscence starts a short distance below the apex in one of the lines of thin-walled cells and extends somewhat in a vertical direction (Fig. 1). The opening may remain as a narrow slit or the sides may flatten out to a spatula shape, which later may become bent or twisted. Only occasionally does splitting take place on the other side also and extend right to the apex, in which case the valves often twist spirally (Fig. 2). The pale yellow page 67
As far as is known A. coriaceus is endemic to New Zealand. It differs from A. laevis in the papillate epidermis, the form of the chloroplasts, the plate-like gemmae, the generally shorter capsule which often opens on one side only, and the surface marking of the spores.