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Some foliose lichens attach only at a single stout peg called a holdfast, typically located near the lichen's centre. Lichens with this structure are called "umbilicate". [31] In general, medium to large epiphytic foliose lichens are moderately sensitive to air pollution, while smaller or ground-dwelling foliose lichens are more tolerant. [37]
Crustose lichens on a wall Growth of crustose lichen on a tree trunk. Crustose lichens are lichens that form a crust which strongly adheres to the substrate (soil, rock, tree bark, etc.), making separation from the substrate impossible without destruction. [1] The basic structure of crustose lichens consists of a cortex layer, an algal layer ...
A foliose lichen is a lichen with flat, leaf-like lobes, which are generally not firmly bonded to the substrate on which it grows. It is one of the three most common growth forms of lichens. It typically has distinct upper and lower surfaces, each of which is usually covered with a cortex ; some, however, lack a lower cortex.
In squamulose lichens the part of the lichen thallus that is not attached to the substrate may also appear leafy. But these leafy parts lack a lower cortex, which distinguishes crustose and squamulose lichens from foliose lichens. [44] Conversely, foliose lichens may appear flattened against the substrate like a crustose lichen, but most of the ...
A crustose lichen, Caloplaca marina. Crustose is a habit of some types of algae and lichens in which the organism grows tightly appressed to a substrate, forming a biological layer. Crustose adheres very closely to the substrates at all points. Crustose is found on rocks and tree bark. [1]
Verrucariaceae is a family of lichens and a few non-lichenised fungi in the order Verrucariales. The lichens have a wide variety of thallus forms, from crustose (crust-like) to foliose (bushy) and squamulose (scaly). Most of them grow on land, some in freshwater and a few in the sea.
The lower cortex of foliose lichens often bears rootlike fungal structures known as rhizines, which serve to attach the thallus to the substrate on which it grows. Lichens also sometimes contain structures made from fungal metabolites, for example crustose lichens sometimes have a polysaccharide layer in the cortex. Although each lichen thallus ...
The Physiaceae family includes various growth forms such as foliose, fruticose, squamulose, stipitate, crustose, and even evanescent types (where certain parts, such as basal squamules, become less noticeable or disappear over time as other structures develop). Some members of this family may also be lichenicolous, meaning they grow on other ...