1. Riccia ciliata Hoffm.

Description of the Plant

The plants are found on soil as greyish-green or glassy-green rosettes up to 3cm in diameter (Fig. 1). Branches are up to 3mm long and 0.6-0.8mm wide. The upper surface of the thallus is flat or convex except for a narrow median groove near the apex. Under a magnification of X 10 or higher it appears marked out into squares. Acicular spines, 0.6-0.9mm long and with a basal width of 40-60μm. project from the margins. They have thick walls which, when swollen with water, tend to be internally tuberculate. On the under side of the thallus there are hyaline median scales, smooth rhizoids of diameter 18-30μm and tuberculate rhizoids of diameter 10-18μm.

Plants are monoicous. The spores have plate-like reticulate markings along with numerous papillae. They have a diameter of 70-90μm, occasionally up to 110μm (Fig. 2a and b).

Anatomy of the Thallus

In transverse section the thallus is approximately the same depth of 0.3-0.4mm throughout. The epidermis consists of hyaline, thin-walled cells which at first are of spherical or conical shape but later shrivel and flatten. The photosynthetic tissue is composed of columns of cells separated by vertical air canals, and beneath is a compact tissue of hyaline cells.

Distribution

R. ciliata is widely distributed in Europe. Probably it has been introduced to New Zealand.

It was collected from seepage areas on the shore of Lake Pukaki where it was growing with other species of Riccia, E. O. Campbell, R. and Y. Elder 30.3.1975 MPN 17033. page 223

R. ciliata
Fig. 1: Part of a rosette.
Fig. 2: Scanning electron micrographs of spores: (a) distal face, (b) proximal face.

2. Riccia crozalsii Levier

Description of the Plant

The plants are found on soil as firm, green rosettes up to 1.5cm in diameter or as large irregular colonies (Fig. 3). Branches are up to 4mm long and up to 1 mm wide. The thallus at a magnification of X 10 or higher often appears spongy due to the spherical, hyaline, epidermal cells (Fig. 4). In older parts it has a flat or slightly convex surface, but near the apex it rises steeply on either side of a well-defined narrow median groove. Hyaline, sharp-pointed cilia, up to 0.5mm long, project from the margin or incurve over the thallus, but they often wither early and are invisible when plants are flooded with water. Their surface, particularly in the upper part, is minutely tuberculate. On the under side of the thallus are smooth rhizoids of diameter 8-21μm, tuberculate rhizoids of diameter 10-18μm and small, delicate hyaline scales. Branching is by forking at the apex and occasionally by adventitious branches. page 224

R. crozalsii
Fig. 3: Part of a colony.
Fig. 4: Scanning electron micrograph of the surface of the thallus after freeze-drying.
Fig. 5: Scanning electron micrograph of spores.

Plants are monoicous. The dark brown spores have triradiate and reticulate markings and truncate, papillate projections. There are conspicuous germ-pores and a broad wing (Fig. 5).

Anatomy of the Thallus

The thallus in transverse section is 0.4mm deep. The dorsal epidermis consists of more or less spherical, hyaline cells. A few of the lowermost cell layers are also colourless. The rest of the thallus is a rather compact, photosynthetic tissue of subspherical cells with air spaces between them.

Distribution

R. crozalsii is known from the western part of Europe, the Canary Islands, and the Cape Province of South Africa (Arnell, 1963); from Israel (Proskauer, 1953); from South India (Udar, 1957) and from South Australia and New South Wales (Seppelt, 1974). In New Zealand it is very plentiful near paths on Rangitoto Island, Auckland, E. O. Campbell 17.8.74 MPN 17018, and it also grows along with other Riccia species on the summit of Mt. Eden, J. E. Braggins, E. O. Campbell and E. Miller 16.8.74 MPN 17016.

Notes

Some forms of R. crozalsii are not readily distinguishable from R. bifurca and the spore morphology of these two species corresponds closely. A detailed study has been made by Seppelt (1974).

3. Riccia glauca L.

Description of the Plant

The plants grow on soil as glaucous-green rosettes up to 3cm in diameter or as irregular colonies (Fig. 6). Branches are strap-shaped, up to 10mm long and 1-1.5mm wide. The upper surface of the thallus is flat in older parts but near the apex has a broad, shallow median groove. In young parts it has a glistening appearance and later shows a fine polygonal pattern (Fig. 7). On the under side of the thallus are delicate, hyaline scales which reach to the margin and both smooth and tuberculate rhizoids.

The plants are monoicous. The spores, of diameter 75-90μm, have a broad wing and show reticulate markings with papillate projections on the distal face (Fig. 8).

Anatomy of the Thallus

The thallus in transverse section is 0.3-0.6mm deep. The dorsal epidermis consists of either one or two layers of thin-walled, hyaline cells. Those of the outermost layer vary from pear-shaped to rounded and tend to collapse early. Those of the underlying layer persist but do not become thick-walled as in R. sorocarpa. Beneath the epidermis is a photosynthetic tissue, which consists of columns of cells enclosing narrow, vertical air canals, while the lowermost third of the thallus is a compact, hyaline tissue. page 226

R. glauca
Fig. 6: Part of a rosette.
Fig. 7: Scanning electron micrograph of the surface of the thallus after freeze-drying.
Fig. 8: Scanning electron micrograph of a spore (distal face).
R. sorocarpa
Fig. 9: Scanning electron micrograph of a spore (distal face).
Fig. 10: Transverse section of the upper part of the thallus: (a) young stage, (b) older stage.

Distribution

R. glauca is found in Europe, America, Asia and Africa. Watson (1959) states that it is perhaps the commonest British Riccia species. Probably it has been introduced into New Zealand.

It was collected from seepage areas on the shores of Lake Pukaki, growing amongst other Riccia species, E. O. Campbell, R. and Y. Elder 30.3.1975 MPN 17035.

4. Riccia sorocarpa Bisch.

Description of the Plant

The plants occur on soil, usually as glaucous-green rosettes or partial rosettes which are 4-9mm in diameter and 2-4 times dichotomously branched. Occasionally there are irregular colonies. Branches are 1-2mm broad. They are narrowed towards the subacute apex and here show a deep and narrow median furrow which becomes less pronounced in older parts. At a magnification of X 10 or higher the upper surface in young parts appears glistening after the manner of R. crystallina. In older parts, after the outermost cells have been destroyed, the surface appears marked into squares. On the under side there are small, hyaline scales which reach to the margin and both smooth and tuberculate rhizoids. Plants are monoicous. The spores are about 80μm in diameter. On the distal face they show reticulate markings with high papillae in the corners (Fig. 9) and on the proximal face they show short, low ridges and a triradiate marking.

Anatomy of the Thallus

The thallus is 0.3-0.6mm. deep. The dorsal epidermis, which provides a useful diagnostic feature for this species, consists of two layers of hyaline cells. The conical or pear-shaped cells of the outer layer are soon destroyed, leaving intact the underlying layer of thick-walled cubical cells (Fig. 10a and b). The lower half of the thallus consists of thin-walled hyaline cells arranged compactly. The rest is a photosynthetic tissue in the form of columns of cells enclosing narrow air canals.

Distribution

R. sorocarpa is widely distributed. It is well known in Europe, North America, Japan, Siberia, North and South Africa (Arnell, 1963). It is reported also from South America (Hassel de Menendez, 1962), from the Sikim Himalayas (Udar, 1956) and from Australia (Seppelt, 1974). In New Zealand it has been found growing with other Riccia species in seepage areas on the shore of Lake Pukaki, E. O. Campbell, R. and Y. Elder 30.3.1975 MPN 17038.

Notes

R. sorocarpa may be indigenous to New Zealand, for Mitten (1855) recorded R. acuminata Tayl, as collected by Colenso in page 228

R. bullosa
Fig. 11: Part of a colony.
Fig. 12: Scanning electron micrograph of the surface of the thallus after freeze-drying.
Fig. 13: Scanning electron micrograph of a spore: (a) proximal face, (b) distal face.

Hawke's Bay. The type packet of R. acuminata (Melb. 19974) was examined by O. Na-Thalang (1970) and by R. D. Seppelt who found that it contained both R. sorocarpa and R. lamellosa. Seppelt notes that, since Taylor's description (1846) is based on mixed material, the name R. acuminata becomes a nomen confusum and by Art. 70 of the International Code of Botanical Nomenclature must be rejected (Seppelt, 1974).

In the Colenso Herbarium of the National Museum of New Zealand there is a specimen which is almost certainly a duplicate of the R. acuminata Tayl. listed by Mitten (1855). This specimen was examined superficially and is considered to be R. sorocarpa. Despite a thorough search in the spring of 1974 no plants of Riccia were found in Hawke's Bay.

Riccia bullosa Link

Description of the Plant

The plants are found on soil, usually as strap-shaped thalli up to 13mm long and up to 4mm wide, once or twice forked; occasionally as rosettes, partial rosettes or large irregular colonies. The colour is green or olive-green above and either green or reddish-purple below. The upper surface is generally flat or convex, with a deep, narrow median groove near the apex, and has thin edges which tend to be hyaline and crenate. Under a magnification of X 10 or higher it is seen to be marked out into polygonal areas whose boundaries represent partitions between sub-epidermal air cavities (Fig. 11). Air pores show clearly in scanning electron micrographs (Fig. 12). The under surface carries both smooth and tuberculate rhizoids, and near the apex a few delicate, hyaline scales which reach to the thallus edge. However, sometimes, as mentioned later, scales do not develop.

In regard to their sexual nature some plants are definitely monoicous, in others only antheridia or only archegonia are present, while many plants are sterile. The brown spores, 0.08-0.1mm in diameter, have a crenate wing and show reticulate and a faint triradiate marking. The areolae on the distal face have a thin border with higher and thicker ridges at the corners; those on the proximal face are ill-defined (Fig. 13a and b).

Anatomy of the Thallus

The thallus shows differentiation into epidermis, spongy tissue. and compact ventral tissue. In transverse section it is 0.6-0.8mm deep in the central region but gradually narrows laterally to a wing-like edge only one cell deep (Fig. 14). The cells of the upper epidermis tend to be hyaline around the air pores. Beneath is a spongy photosynthetic tissue, which in the central region is 0.15mm deep and is composed of vertical partitions separating narrow air canals (Fig. 15), and nearer the margin is 0.3-0.45mm deep and consists of unistratose partitions between what appear as two or three layers of wider air cavities (Fig. 16). The ventral tissue, 0.2-0.4mm deep, is green in young plants of the thallus but has only a few chloroplasts in older parts.

Distribution

Riccia bullosa is found in South Africa (Sim, 1926; Arnell, 1963). In the North Island of New Zealand it has been collected in the page 230 Auckland province from Pio Road, Waihi Beach, J. E. Braggins 4.11.1973, MPN 17014; from the crater of Mt. Eden, E. Miller 25.10.1973 MPN 17013; from Epsom Road, Auckland, J. E. Braggins, E. O. Campbell, E. Miller 16.8.1974 MPN 17019; from the bowling green at Coromandel, E. O. Campbell 20.4.1975 MPN 17032. In the South Island it his been collected in Canterbury from the shore of Lake Pukaki, E. O. Campbell, R. and Y. Elder 30.3.1975 MPN 17034 and from Glenariffe, Upper Rakaia River, A. J. Healy 8.4.1974 MPN 17039.

Notes

As a result of a comparison between herbarium specimens of R. bullosa from South Africa and plants collected in New Zealand it was concluded that the species exhibits a considerable degree of polymorphism. Plants from South Africa tended to be firmer due to epidermal cells with somewhat thickened walls. In plants from the South Island of New Zealand the air pores were less clearly defined than in those from the North Island and the cells surrounding them tended to disintegrate in older parts of the thallus. Also scales failed to develop. Lack of scales was found also in plants collected in the North Island and grown in culture under conditions of high humidity and cool temperature.

As was noted by Arnell (1963), the structure of the thallus in R. bullosa is intermediate between that of the subgenus Riccia and the subgenus Ricciella. There are narrow air canals in the central region and much wider air cavities nearer the margin. This type of structure is found also in R. vesiculosa Carr. and Pears., as noted by Stephani (1898-1900). The range of R. vesiculosa is given as New South Wales, Queensland, Northern Territory (Na-Thalang, 1970).

Carrington and Pearson (1887) mention the close similarity of R. vesiculosa to R. bullosa but the latter is stated to be dioicous (Sim, 1926; Arnell, 1963) in contrast to the reported monoicous condition of R. vesiculosa (Stephani, 1898-1900; Na-Thalang, 1970). The sexual nature of the New Zealand plants was found to be very variable.