Description
Members of Catillariaceae have a very variable body (thallus). Most are crust-forming lichens that stick tightly to the substrate, sometimes splitting into a network of cracks ( rimose ), breaking up into little warts or blocks ( areolate ), forming small scales, or spreading with a rosette-like edge ( placodioid ). A few are fruticose, meaning they grow as small, branched tufts. In some taxa the thallus is partly sunk into the substrate or so thin that it fades away; lichenicolous species that live on other lichens may lack a thallus altogether. The photosynthetic partner is a simple green alga with small, spherical cells (a chlorococcoid photobiont). [3]
The fruiting bodies are apothecia, usually brown to black and typically without a frosted coating ( pruina ). A rim made from the thallus (the thalline margin ) may be absent from the start, or present when young but later pushed aside as the disc expands. The true margin of the apothecium (the exciple ) is well developed in most species, at least in young stages; it is made of radiating, branched fungal threads and holds together firmly, including in standard chemical tests used by lichenologists. Inside the disc, the tissue between the spore-bearing sacs (the hamathecium ) consists of straight or only slightly branched threads (paraphyses) whose tips are abruptly swollen and capped with dark brown pigment. [3]
The asci (spore sacs) usually contain eight spores (occasionally up to sixteen) and are cylindrical to club-shaped. They show a characteristic Catillaria-type reaction in the iodine–potassium test used in microscopy: a blue outer coat and a uniformly blue dome at the tip, and in some cases a small clear ocular chamber is visible at the apex. The ascospores are typically colourless, divided by a single cross-wall (1-septate), and lack any gelatinous outer sheath. Asexual reproductive structures (pycnidia) are common but often hard to see because they are sunk into the thallus; they produce colourless, non-septate conidia (asexual spores) that are ellipsoidal to rod-shaped. The conidia arise from producing cells that may be linked in chains with spores budding from the ends and sides, or arranged in a single layer of broadly flask-shaped cells. [3]
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