Aloina Kindberg, 1882, nomen conservandum

Aloina are small plants of seasonally dry soil. The plants have deeply concave leaves whose margins are incurved. The cup-shaped leaves enclose a patch of photosynthetic filaments that are so closely placed as to appear to be a deep green cushion. Smooth but more or less quadrate median laminar cells combine with an often obscure capsule to make the plants seem unusual within the Pottiaceae.

Key to Aloina

Species included in this key are in the Pottiaceae:
Aloina aloides, not known from CA
Aloina ambigua (Bruch & W. P. Schimper) Limpricht
Aloina bifrons (De Notaris) Delgadillo
Aloina rigida (Hedwig) Limpricht
Aloina roseae (Williams) Delgadillo, not known from CA

Among California mosses, there are three genera of very small mosses with various patterns of photosynthetic processes on the adaxial surface of the costa. Pterygoneurum has sheets of cells (lamellae) on that costa, and these lamellae may remind one of the arrangement of the photosynthetic lamellae in the Polytrichaceae, a family of consistently larger plants. Crossidium and Aloina have a cushion of closely arranged filaments. Aloina is easily distinguished from Crossidium: the former has margins that inflex over and partially obscure the cushion of photosynthetic filaments; the latter has reflexed to recurved leaf margins.

A. Leaf with hyaline awn .....B
A. Leaf muticous with costa ending before apex or percurrent .....C

B. Costa cross-section lacking stereid bands, costa therefore hard to distinguish from adjacent cells .....Aloina bifrons
B. Costa present and well-defined; stereid bands in cross-section several cells thick .....Aloina roseae not known from CA

C. Marginal cells of leaf base similar to adjacent interior cells .....Aloina ambigua
C. Cells of basal margin of leaf hyaline and thin-walled, often elongate, forming a well-demarcated limbidium .....Aloina rigida