“Lichens? They are just wannabe plants!” as one of my past botany students put it – she didn’t like them very much! Well I suppose there is some truth in this. Lichens are a curious combination of an alga (a group of plants which includes the seaweeds) and a fungus (not a plant – in fact fungi (e.g.mushrooms and toadstools) are closer, in evolutionary terms, to animals than to plants!). This cross-taxonomic union is often termed a “symbiosis” because two different organisms appear to be co-operating, the fungus provides the physical structure (the home, made out of fungal threads (hyphae) and the alga (which lives in and amongst the fungal hyphae) provides the food (producing sugars for itself and the fungus via photosythesis). If we delve deeper, we find that this is all a bit more sinister than the cosy notion of symbiosis suggests, but we can leave that discussion for another time!
Whether they are or are are not plants, or a symbiosis of plant and fungus or indeed of plant and animal (;-) need not concern us here, the resulting organisms are, to Dr M’s eye (if not to all of his students!) easily amongst the most extraordinary and beautiful in the living world. Indeed even their curious and taxonomically challenging nature adds to their allure.
Here we have Peltigera horizontalis one of the so-called foliose (leaf-like) lichens which amply demonstrates their beauty and fascination. This is a large lichen of which can be found growing on rocks and in open grassy and mossy areas. When dry this lichen is a light grey (left hand image) and very crispy and brittle in nature, when wet (right hand image) it turns a delicious dark brown and becomes quite rubbery in nature.
More on lichens to come in future posts! Meanwhile, if you come across a weird and wonderful thing which you think might be a lichen, contact Dr M and why not send in a photo for identification?