Home › Volumes › Mosses and Lichens › Herbarium

Leafy Hepatics, Scale Mosses, or Foliose Hepatics

Porella platyphylla (See Colour Plate XIV), is a good example of the foliose or leafy hepatics and from a study of it one may become familiar with the conspicuous parts of this class of mosses.

The plants grow flat upon the bark of living trees. Each plant consists of a creeping stem, with side branches which may in turn bear branches.

The principal leaves are set at right angles to the stem and their sides overlap so as to conceal the stems.

They are two-lobed with one lobe above the stem and one below.

A third row of leaves grows on the underside of the stem.

In some leafy hepatics, the tips of the leaves overlap the base of the leaf in front; in others the tips of the leaves are underneath the bases of the leaves in front.

The margins of the leaves of different species vary, they are recurved, toothed, fringed, inrolled, or entire.

The apex may be blunt or pointed or of many other designs.

The male organs (antheridia) are borne in the axils of the leaves of modified branches.

The female organs (archegonia) are on the terminal branches.

The spore-cases with their enveloping parts are terminal on the branches; although they appear often to be on the sides because a side branch has grown in the same direction and beyond the main stem.

Beginning with the spore-case as a centre, and observing the parts in order outward, a veil (calyptra) may be found, and then a perianth, and outside of all, several slightly modified leaves.

Genus PORELLA, (L.)

The Genus Porella is composed of large plants, dark-green to yellowish-brown, usually 2 to 3 times feather-branched.

The lobes of the leaves are very deeply two-parted; the dorsal large, and roundish egg-shaped, usually entire, the ventral lobes smaller, sometimes nearly separate from the dorsal, varying in different species from ovate to lanceolate; underleaves large, entire or toothed.

The antheridia are spherical, in the axils of overlapping leaves which form short rigid branches.

The perianth is oval to obovate, flattened at the mouth, which is fringed, toothed or entire. The spore-case is spherical to ovoid-oblong on a short stalk (seta) splitting nearly to the base into four parts. The spores are covered with spines. The elaters are once to thrice spiral.

The generic name is a diminutive of the Latin porus, a pore. Its significance is not evident.

Porella platyphylla, (L.) Lindle. Plant (gametophyte).--Stems 2 or 3 inches long, prostrate, rigid with the tips bent upward; 1 to 3 times regularly or irregularly pinnate; root-hairs in tufts at the base of the under-leaves.

Leaves.--Deeply two-parted, dorsal lobes overlapping in two rows so as to conceal the stem, obliquely placed relatively to the stem, oval to oblong, apex obtuse, toothed or entire. Ventral lobes oval to oblong obtuse, diagonally pressed to the surface of the upper lobes; margins recurved and entire or with a single tooth at the base; under leaves tongue-shaped, parallel with the stem, margins recurved, decurrent, entire, or sparingly toothed at the base.

Name.--The specific name platyphylla from the Greek, flat, and, a leaf, describes the prostrate habit of the plant.

Perianth.--Ovate, inflated, narrowed above, margin toothed with a notch on one side.

Veil (calyptra).--Persistent, globose, splitting above.

Spore-case.--Pale yellow-brown on a short pedicel, splitting into four, often irregular valves; elaters bi-spiral.

Spores.--More or less spiny.

Habit of flowering.--Male flowers (antheridia) and female flowers (archegonia) on separate plants (dioicous).

Antheridia.--Spherical, short-stalked, single in the axils of two-lobed, pouch-shaped leaves which lie opposite on the stem. These antheridial leaves are united by their margins to the under leaves, and with them form short oval branchlets on the sides of the main branches.

Archegonia.--Numerous, terminal on very short lateral branches.

Genus FRULLANIA, Raddi

The plants are usually in shades of red or brown or even black, although sometimes green. They grow in delicate traceries over the bark of trees or rocks.

The stems are opaque and branched, each branch arising from the axil of a stem-leaf from which it is always free.

The upper leaves are alternate and are inserted somewhat obliquely. They are two-lobed, one lobe folded to lie over the other. The upper and larger is known as the lobe and the lower and smaller as the lobule.

The lobule, is an inflated water-sac, in shape resembling a helmet or hood or cylinder and often has at the base a tiny process (stylus).

The under leaves or stipules (amphigastra) are strongly two-cleft and have often tufts of rootlets at their bases.

The male flowers (antheridia) are found on short branches either on the same plant with the female flowers (archegonia) or on separate plants.

The envelope of the flower (perianth) is free and exserted from the leaves. It is 3- to 4-angled and tipped with a short tubular beak (mucronate). The veil (calyptra) is free and included in the perianth. The spore-case is somewhat spherical on a stout pedicel 2 to 3 times longer than the perianth. It opens by four valves to eject its spores. There are about 150 species in all, which are well represented in both temperate and tropical zones; about twenty are found in North America.