Systematic Account.
LECIDEACEAE
Thallus crustose, without plectenchymatous cortex ([Fig. 2], a), varying from granulose and often evanescent to conspicuous, areolate, or even subsquamulose conditions, attached to the substratum by hyphal rhizoids ([Fig. 2], d), and in a few instances extending up as a veil and surrounding the apothecia laterally, the hyphae densely interwoven toward the upper surface, but more loosely disposed below ([Fig. 2], a and b); apothecia usually minute or small, commonly rounded, the exciple weak and obscure ([Fig. 10], d), or more strongly developed when conspicuous and much darker in color ([Fig. 11], b); hypothecium varying from hyaline to dark brown ([Fig. 10], b and [Fig. 11], c); hymenium almost always lighter and commonly hyaline (Figs. [10] and [11], a); paraphyses usually simple, but branched forms to be found frequently (Figs. [1] and [12]), pale throughout or darkened toward the sometimes enlarged apex, commonly more or less coherent and indistinct at maturity; spores simple and hyaline to muriform and brown (Figs. [2], [3], [4], [5], [6], [7], [8], [9], and [13]).
KEY TO THE GENERA
| Spores minute, numerous in each ascus | Biatorella, p. |
| Spores larger, usually 8 in each ascus, | |
| Spores hyaline. | |
| Spores one-celled (simple) | Lecidea, p. |
| Spores more than one-celled (compound). | |
| Spores 2-celled | Biatorina, p. |
| Spores 4- to several-celled. | |
| Spores ellipsoid, fusiform, or dactyloid | Bilimbia, p. |
| Spores acicular | Bacidia, p. |
| Spores brown, or becoming brown. | |
| Spores 2-celled | Buellia, p. |
| Spores 4-celled and becoming muriform | Rhizocarpon, p. |
Biatorella De Not. Giorn. Bot. Ital. 21. 192. 1846.
Thallus granulose to verrucose and subareolate, sometimes inconspicuous and evanescent; apothecia minute to middle-sized, adnate or more or less immersed, exciple usually prominent and persistent, but sometimes becoming covered, disk flat to convex; hypothecium and hymenium pale to brown; spores simple, hyaline, minute, numerous in each ascus.
KEY TO THE SPECIES OF BIATORELLA
| The whole apothecium dark colored | 1. B. simplex |
| The disk of the apothecium white-pruinose | 2. B. pruinosa |