Sticta torii is a lichen with cyanobacteria (genus Nostoc) as its primary photosynthetic partner. It lacks a stalk and has an irregular thallus that can grow up to 1.5–2.0 cm in diameter. Initially single-lobed, it eventually becomes multi-lobed and is quite fragile. The lobes are rounded to elongate, often ascending but sometimes curving downward at the tips, and are imbricate (overlapping like roof tiles). Secondary lobes can be involute (rolled inward), with margins sometimes featuring lacerate (torn) outgrowths of isidia (small, finger-like reproductive propagules). The upper surface is smooth, gray to dark brown, and may be matt or somewhat shiny, with occasional sparse maculae (spots) near the tips.[2]
Isidia are present and abundant, primarily along the margins but also on the surface, growing into branching, tree-like structures up to 0.6 mm long. The medulla (inner layer) is compact and white. The lower surface is even and cream to brown-colored, with dense tomentum (hairy layer) that becomes sparser toward the margin.[2]
Sticta torii has no rhizines (root-like structures) but features sparse cyphellae (small, pore-like structures) scattered throughout, which are rounded to irregular with wide pores. The upper cortex is 25–55 μm thick, consisting of 2–4 layers of cells. The photobiont layer is 35–65 μm thick, while the medulla is 110–240 μm thick. The lower cortex is 25–45 μm thick, also with 3–4 cell layers. The lower tomentum consists of unbranched, cylindrical hyphae in bundles, with occasional moniliform (rosary-like) appearance near the margins.[2]
