Genus OrthotrichumGenus ORTHOTRICHUM, Hedw.
The species of the Genus Orthotrichum grow in round cushions on rocks, trees and walls. The plants are usually erect, with branching stems having radicles at the bases.
The leaves are lance-shaped, lapping like shingles, rarely twisted when dry, the surface is covered with minute protuberances, or is rarely smooth in the upper part; the margin is recurved; the cells toward the apex of the leaf are dot-like and contain chlorophyll, toward the lower part they are longer and transparent; the veil is bell-shaped, more or less split at the base and keeled or deeply grooved throughout, it may be naked or may have a few straight hairs, a character which suggested the name Orthotrichum, from the Greek for; straight, and; hair.
The spore-cases are immersed or exserted on a short pedicel and have usually, when dry, 8 to 16 grooves running lengthwise, but they may be smooth.
The pedicels are generally short with an enlarged base (vaginule) crowned with a minute cup-like sheath. The peristome is simple or double, the outer consisting of 16 single teeth or 8 pairs, with either no annulus or a very narrow one.
In all there are two hundred and thirty-five species, fifty-seven being found in North America.
Orthotrichum Strangulatum Moss