Cladonia portentosa (Dufour) Coem. forma portentosa
Cladonia impexa Harm. nom. illeg.
General description: Primary thallus crustose, evanescent, most often absent. Secondary thallus up to 10 cm tall, forming compact delicately interwooven mats, and large cushions with neighbouring colonies, very richly branched, axils are often perforate, highly and trichotomously ramified (sometimes the last division is dichotomous), short branchlets spreading out in all directions, surface smooth, pale grey-greenish, cream, very pale whitish when moist and shaded, more yellowish (ivory) in dry and well-lit areas. Apothecia very rare, minute, brown. Photobiont : trebouxioid. Thallus: C-, K-, KC+/- yellow, Pd-, UV+ pale blue. Very common in aerohaline acid heathlands at the base of Calluna, identifiable from far due to its pale colour. Not to be confused with Cladonia ciliata, darker, and Cladonia arbuscula that are Pd+ rusty. This species is extremely variable and sometimes different morphs have been distinguished, however they often can be found in the same location and in the same tuft with a common origin, demonstrating that these different forms belong to the same species.
Cladonia portentosa f. portentosa: 'coralloid' aspect, podetia yellow-greenish when moist, 5-10 cm tall, base of the main branches very thick and distorted, secondary branches short and irregular, usually with pointed ends and pycnidia, Pd-. This form, although selected as the canonical type, is rather rare, grows on humid rocks or in humid areas in woodlands and forests, often together with the darker Cladonia ciliata.
Cladonia portentosa f. condensata: very thin podetia clustured in dense tufts, forming cushions usually yellowish or ivory. This morph is common in well-lit heathlands near the seashore and at the top of rock walls or cliffs.
Cladonia portentosa f. laxiuscula : main branch base thick and robust with fertile branchlets oriented in all directions; it is the most common morph in woodlands and forests.
Cladonia portentosa f. spumosa: main branches thick, topped by short and verticillate branchlets (cauliflower-like).*