About Grimmia laevigata (Brid.) Brid.
Gametophyte: It is dioicous. For the female, the innermost perichaetial leaf is up to 2 mm long. It sheaths up to the broadest part of the leaf, is narrowed at the leaf base, and is ovate to broad - ovate. The lower half is hyaline or has only some rows of hyaline cells at the margin, which vanish at the mid - leaf. The costa is obscure in the apical part and excurrent in a long, denticulate hair - point. The perigonia are multifoliose buds at the tips of branches. For the male, the innermost perigonial leaf is up to 1 mm long, sheathing, broad - ovate, and suddenly narrowed to an acute apex with a hyaline cell. It is hyaline in the lower part, and the costa vanishes below the apex. The paraphyses are short and numerous. The growth form has a lax cushion. Young shoots are mostly present, originating from decomposing plants, with scale - like leaflets appressed to the stem. The costa vanishes below the acute apex, with a sharply pointed hyaline cell or short hair - point. The plants are erect, scarcely branched, slightly radiculose at the base, and the stems are up to 20 mm high with a well - developed central strand. The leaves in the lower part of the stem are scale - like, gradually getting longer towards the tip of the stem, 1.2 - 1.8 mm long, rarely up to 3 mm long. They are imbricate, appressed to the stem when dry. Older leaves bend backwards when moistened, and younger leaves move slightly, being erect or spreading when wet. They start from a short (about 1/5 of leaf length), rounded, half - sheathing, slightly decurrent leaf base, are lingulate or broad - lanceolate, and taper to an obtuse, rounded, or even acute apex. The hair - point is roughly denticulate, occasionally nearly smooth. The leaf form in situ is widely concave or concave throughout, and the margin is plane. Some rows of basal paracostal cells are rectangular with smooth or faintly nodulose walls. Towards the margin in the sheathing part, the cells are isodiametric, transversely rectangular, or oval, with transverse walls thicker than longitudinal walls. In the laminal part, the cells are homogeneous, rounded, and have thick walls. The leaf base, in transverse section, is unistratose, bistratose in places in the transitional part, and bi - to tristratose in the laminal part. At the margin from the insertion up to the apical part, one or more cell rows are unistratose, at least one side is unistratose in the apical part, and it is bistratose at the apex. The costa, seen on the dorsal side, is large at the leaf base, indistinct from above the widest part of the leaf up to the apex, and excurrent. In the laminal part, the dorsal cells are not different from the lamina cells. In transverse section, on the dorsal side at the insertion and lower part of the leaf, it is flat or weakly convex, and slightly rounded in the upper part. On the ventral side, it is widely channelled at the leaf base and narrowly so in the upper part. At the insertion and leaf base, there are 7 to 11 ventral cells, most of which are guide cells, with a small median band of substereids interrupted by 3 groups or one large central group of hydroids. The substereids and hydroids vanish in the apical part. In the transitional part, the number of guide - cells is reduced to 4, and in the laminal part, there are 2 guide cells sunken into a narrow channel with strongly thickened adaxial cell walls. Sporophyte: The seta is up to 3 mm long and straight, and the vaginula is 1 mm long and cylindrical. The capsule is emergent, obloid, and smooth. The exothecial cells are elongated, of variable shape, slightly curvilinear. The stomata are in the short neck, and the annulus consists of three rows of cells that detach spirally in groups. The calyptra is mitrate, brownish in the upper part, lobed, and covers the upper part of the capsule. The operculum is conical, with a straight, blunt beak, an uneven or crenulate margin, one or two marginal rows of rounded cells, and irregular, thick - walled, curvilinear, faintly nodulose cells in the conical part. The peristome teeth are erect when dry, broad at the base, slit half - way down to two or three branches or perforate. The lower dorsal side is smooth, and the upper dorsal and ventral sides are sparingly to densely covered with rounded papillae. The trabeculae are broad, distant, protruding, and thin in the upper third. It matures in September. The spores are 12 - 16 µm and smooth.
