Cladonia macilenta Hoff. (syn. C. bacillaris Nyl.)

Habitat Picture

Figure 1. Cladonia macilenta (PLP847_2018_186) found on dead wood in a northern dry pine forest in Michigan’s upper peninsula (Luce County).

Cladonia macilenta Hoff. (Ascomycota, Cladoniaceae) is a widely distributed fruticose lichen found primarily on dead wood and tree bases, but occasionally over soil and rocks (Fig. 1). The species has a twofold thallus. The primary thallus is squamulose (separate or overlapping scales). Light-brown, erect and stalk-like podetia (4 to 35 mm in length) arise from the primary thalli (Fig. 2A). Typical of the Cladoniaceae family podetia are hollow (Fig. 2B). In C. macilenta podetia are also sorediate (responsible for their green appearance), rarely branched, do not form cups and have sporadic squamules.  Lichens are symbiotic associations between fungi (ascomycete) and algae or cyanobacteria. In the case of C. macilenta, its photobiont is a green alga. Green algae cells are intertangled in fungal hyphae to form globose, farinose soredia nearly continuous over the entire podetia and uniform in size (Fig. 2C). Apothecia are rare. Instead, soredia serve as the primary vegetative propagule.

Micro - characteristics

Figure 2. Cladonia macilenta (PLP847_2018_186) podetia arising from squamulose primary thalli (A). A hollow podetium, typical characteristic of the Cladoniaceae family (B). Powdery, globose bundles of hyphae and green algae (soredia) covering the podetia (C).

Other comments: Reported to occasionally contain usnic acid. Usinc acid is a secondary metabolite unique to lichens with potential commercial application in the fields of cosmetics, medical, perfumery and nutrient supplements. Also, chemical spot tests for the specimen presented here (PLP847_2018_186) were PD – (para-phenylenediamine) and K -(potassium hydroxide). Two chemical races of C. macilenta are often described. The first chemical race is PD-, K-, C – (sodium hypochlorite) and KC + yellow to orange, and is sometimes reported as C. bacillaris. While, the second chemical race is PD+ orange, K + yellow, KC-, and C-.


Taxonomy: Ascomycota, Lecanoromycetes, Lecanorales, Caldoniaceae, Cladonia, macilenta.



Brodo, I. M. 2016. Keys to lichens of North America: revised and expanded. Yale University Press, New Haven, CT.

Brodo, I. M., Sharnoff, S. D., and Sharnoff, S. 2001. Lichens of north America. Yale University Press, New Haven, CT.

Ingolfsdottir, K. 2002. Usnic acid. Phytochemistry 61:729-736.


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