Description: Phymatolithon is a genus of non geniculate coralline red algae, known from the UK and Australia. It is encrusting, flat, and unbranched; it has tetrasporangia and bisporangia borne in multiporate conceptacles. Some of its cells bear small holes in the middle; this distinctive thallus texture is termed a "Leptophytum-type" thallus surface, and has been posited as a taxonomically informative character. It periodically sloughs off its epithallus, reducing its overgrowth by algae by as much as 50% compared to bare rock. https://en.wikipedia.org/wiki/Phymatolithon
Phymatolithon 1992-06-18