Platyhypnidium riparioides (Long-beaked Water Feather-moss) is a species of aquatic moss

Moss

Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...

 commonly found in many regions. This species is among the largest aquatic mosses growing up to 15 cm long. P. riparioides grows in a procumbent or pendulous fashion along rocks and tree roots and may form extensive lax mats of many intermingled plants. It is widely distributed South of the Arctic and can grow abundantly in suitable areas.

Description

Platyhypnidium ripariodes is among the larger northern hemisphere mosses with leaves up to 8mm long and plants growing up to 15 cm long. In the UK, plants commonly produce calyptra

Calyptra

Calyptra is a scientific term used in botany. It describes a feature in plant morphology.-Bryophytes:In bryophytes, the calyptra is an enlarged archegonial venter that protects the capsule containing the embryonic sporophyte . The calyptra is usually lost before the spores are released from the...

with relatively long curving lids. The leaf tip is acute, leaf margins are plane, slightly denticulate towards tip, mid-leaf cells are large, costa or the central stork of the leaf extends nearly to leaf tip. The growth form is procumbent but small, young plants can attach themselves closely to rocks and appear flattened.

Identification

Platyhypnidium ripariodes diagnostic features include its comparatively large size, up to 15 cm long, large leaf size up to 8 mm with elongated mid-leaf cells. Capsules are abundant and frequently produced and feature long curving lid. In the UK, mosses growing in similar habitats and maybe confused with P. ripariodes include aquatic Brachythecium genus and Leptodictyum riparium. All these mosses are platycarpus, have a single nerve per leaf and overlap in size but can be separate by leaf shape, cell structure and growth form.

Distribution

Wide global distribution found South of the Arctic polar region in flowing freshwater mainly in Northern Hemisphere. Found commonly in the British Isles.