Apothecium (pi. apothecia) a spore producing organ which is open and more or less concave or convex; may be disk-like, saucer-shaped, or irregular, see Fig. 22(A &c B), p. 26.
Crustose a lichen growth form; thalli crust-like, growing in direct contact or buried within the substrate; lacking a lower surface layer and rhizines. see Fig. 9, p. 14.
Foliose a lichen growth form; thalli leaf-like, flattened, with both an upper and a lower surface; usually attached to the twig by rhizines which grow from the lower surface, see Figs. 10 &: 12, pp. 15 & 17.
Fruticose a lichen growth form; thalli shrubby or hairy; standing upright from the twig or dangling from it; usually attached at a single point. see Figs. 17 &: 18, pp. 22 &: 23.
Hyphae the thread-like elements of a fungal body.
Isidium (pi. isidia) fragile, finger-like or irregular outgrowths from the surface of the thallus. The isidia break easily and their fragments can produce a new lichen, see Fig. IIB, p. 16.
Rhizines strands of hyphae extending from the lower surface of a thallus; found on many foliose lichens, see Fig. II A, p. 16.
Soralium (pi. soralia) a group of soredia on the surface or margins of the thallus; conspicuous clumps of soredia occuring in definite patterns on the thallus. see Fig. 7 (A &: B), p. 12; Fig. IOB, p. 15.
Soredium (pi. soredia) erupt from the surface of the thallus in patches, mounds, or piles called soralia. Individual soredia are so small that they are almost invisible even with a hand lens, but in groups they give the surface of the soralia a powdery appearance, see Fig. 15A, p. 20; Fig. l6A, p. 21.
Substrate the surface on which the lichen grows. In the case of the lichens in this guide, normally the substrate is the surface of a twig.
Thalline margin a rim around an apothecium which contains algae and which resembles the surrounding thallus in color and texture. A thalline margin usually differs in color from the disk of the apothecium. see Fig. l4(A &: B), p. 19.
Thallus (pi. thalli) the plant body of a lichen.