Asplenium scolopendrium

Nothing else really looks like hart's tongue. It is a member of the genus Asplenium - the spleenworts - but all the other spleenworts have deeply divided blades, and on appearance you wouldn't think they were closely related at all.

Perhaps the most similar looking fern is adder's tongue - Ophioglossum vulgatum. However, the sori of Ophioglossum vulgatum are borne on separate bladeless spikes whereas the sori of Asplenium scolopendrium occur in straight lines along the veins.

What is a sori? Well a sori is really a sorus when there's only one of them.

A sorus is a parcel of sporangia. But what is a sporangia? Well a sporangia is really a sporangium when there's only one of them.

A sporangium is a little parcel in which spores are formed. Spores are asexual reproductive structures containing a single set of chromosomes. They grow into fern gametophytes, which are are strange things indeed.

The bit of a fern we're used to seeing is actually the sporophyte, which is diploid - like you and me.

Anyway, the sori are the long lines of rust-coloured sporangia which we can see in the top picture. No other native fern has an undivided blade with sori which look like this.

It's always nice to look for something you don't need even a hand lens to identify - Asplenium scolopendrium can be found in a range of wet, shaded habitats which aren't too acidic. This plant was growing on a part of the aqueduct from Loch Katrine to Glasgow.