5. Indusiella Brotherus & Müller Hal., Bot. Centralbl. 75: 322. 1898.
[Latin indusium, tunic, and -ella, diminutive, alluding to inrolled hyaline leaf margins]
Patricia M. Eckel
Plants (6.5-)7-9 mm, succulent, in dense cushions, brownish and translucent proximally, succulent, blackish green and opaque distally. Leaves ellipsoid-ligulate, leaf limb ligulate and tubulose-fistulose beyond a flat, flaring and sheathing base, apex cucullate-fistulose; lamina beyond the base spirally inrolled, 2-stratose except for a margin 2- or 1-stratose in several rows, adaxial cells and cells of inrolled margins thin-walled, hyaline, strongly chlorophyllose, muticous or minutely apiculate; basal cells heterogeneous, oblate, quadrate and short-rectangular, with straight, somewhat thinner walls than cells in the leaf limb; mid leaf and distal cells quadrate or rectangular, with straight, somewhat thick walls. Gemmae absent. Sexual condition autoicous; perichaetial leaves slightly enlarged. [Seta short, straight. Capsule erect, shortly exserted, symmetric, subglobose; annulus differentiated, of small non-vesciculose, quadrate, thin-walled cells, persistent; operculum long-rostrate, falling detached from the columella. Calyptra campanulate-mitrate, not erose, deeply lobed, large, covering the entire capsule, deeply plicate.]
Species 1: Alaska, Asia, Africa.
Affiliation of Indusiella with the Grimmiaceae is most evident in the large, campanulate-plicate calyptra and rather short, cribrose peristome. The thickened transverse basal cell walls contrasted with the thinner longitudinal walls are typical of many species of Grimmia, though also of Encalypta. Indusiella is the only genus in the Grimmiaceae with specialized photosynthetic modifications in the leaf blade, although the family contains one other monotypic genus, Aligrimmia R. S. Williams of arid regions of Peru, with peculiar costal lamellae that apparently enhance photosynthetic capacity. Enhanced laminal photosynthetic tissue within rolled laminal margins is, however, also characteristic of a few species in the pottiaceous genera Hilpertia, Pseudocrossidium, and Tortula. Although the habit and leaf shape of Indusiella closely resemble those of Aloina and Crossidium in the Pottiaceae, it lacks the filaments on the adaxial surface of the costa that are characteristic of those genera. B. M. Murray (1984) discussed xeromorphic specializations of genera in both families as well as phytogeographic considerations relevant to a relict Beringian flora on slopes along the Yukon River basin along the Alaska-Canada border where the North American collection of Indusiella was made.
Indusiella is found in arctic-alpine, high altitude desert and steppe regions.
Murray, B. M. 1984. A revision of the monotypic genera Indusiella, Aligrimmia and Coscinodontella (Musci: Grimmiaceae), with comments on convergent xeromorphological features. Bryologist 87: 24-36.