Leucobryum Moss

Plant / epiphyte
Leucobryum glaucum grows on trunk of Trees with bark of low pH

Foodplant / saprobe
fruitbody of Lindtneria leucobryophila is saprobic on dead Leucobryum glaucum

Plant / associate
fruitbody of Russula silvestris is associated with Leucobryum glaucum

The collection from Alberta (Drummond’s Musci Americani 89, TENN) is probably incorrectly labeled as to locality.

Large, tall cushions distinguish Leucobryum glaucum and under favorable circumstances some cushions may exceed 1 m in diameter. The separation of smaller, shorter plants from L. albidum is difficult. The use of the number of layers of leucocysts on both sides of the chlorocysts is highly variable and not a reliable distinguishing feature. The ratio of length of the sheath to the length of the limb provides the most consistent way to separate L. glaucum from L. albidum. Sporophytes are infrequently observed. Of 1933 collectons examined, 308 (16 percent) had sporophytes. Most of the plants with sporophytes were from collections located north of the Ohio River. Leucobryum antillarum Bescherelle var. antillarum has been reported from the Coastal Plain of the United States based upon plants that had only 1 layer of leucocysts on both sides of the chlorocysts across a wide section of the median portion of the leaf as seen in transverse section near the base. However, this character is quite variable and not even consistent in L. antillarum (H. A. Crum and L. E. Anderson 1981, vol. 2). Also, plants from the coastal plain do not show the prorate cells on the lateral wings of the lamina that are present in the type material of L. antillarum.

Plants often robust, up to 20 cm high, whitish to grayish green, in dense compact tufts or cushions. Stems erect, simple or branched; central strand absent. Leaves erect to erect-spreading or sometimes subsecund, 4–8 mm long, lanceolate to gradually narrowed to subtubulose apices from an oblong-ovate base, acute to apiculate or bluntly mucronate at the apex, dorsal side of leaf acumina smooth; margins entire, bordered by 2–3 rows of linear cells, basal laminae consisting of 5–9 rows of quadrate to rectangular cells; costa in cross section with 2(–3) layers of leucocysts on both sides of chlorocysts in the upper part of leaves, sometime 3(–4) layers of leucocysts on both sides of chlorocysts near leaf base. Dioicous. Setae slender, 2–3 cm long, reddish brown; capsules ovoid, 1.5–2.0 mm long, strongly inclined and curved, strumose; opercula long-rostrate; annuli none; peristome teeth the same as described under the genus.

Plants in tall, compact cushions or turfs. Stems 1-12.5 cm (rarely shorter). Leaves 3-9 mm, limb concave to subtululose, erect or erect-spreading, sometimes falcate-secund, apex acute or apiculate, usually ± serrulate at the tip, spreading from oblong-obovate sheath, 1-2(-3) times the length of sheath; costa in transverse section near base showing lateral, thicker regions composed mostly of 2-3(-4) layers of enlarged leucocysts on both sides of the central layer of chlorocysts and a central, thinner region composed of 1 layer of smaller leucocysts adaxial to and 2 layers abaxial to the chlorocysts (or vice versa), occasionally with only 1 layer of leucocysts on both sides of the chlorocysts; lamina narrow, 5-11 cells wide. Specialized asexual reproduction by clusters of small caducous leaf-like gemmae at stem tip and by leaves with rhizoids at apex. Seta 8-18 mm, reddish. Capsule strongly inclined and curved when dry and empty, usually strumose, 1.5-2 mm, red to reddish brown; operculum 1.5-2 mm; peristome teeth dark red. Spores nearly smooth to minutely papillose, 13-18 µm.

Distribution: widely distributed in temperate and cool temperate regions of the Northern Hemisphere.

Habitat: on humus under coniferous-broadleaf forests.

Dicranum glaucum Hedwig, Sp. Musc. Frond., 135. 1801

Leucobryum glaucum (L.) Schimp. Coroll. BryoL
Eur. 19. 1855.
Bryum glaucum L. Sp. PI. 1118. 1753. Dicranum glaucum Hedw. Fundam. 2: 92. 1782. Leucobryum vulgar e Hampe, Flora 20: 282. 1837.
Pseudautoicous : male plants minute; from 2 to rarely 6 mm. high, growing on tufts of tomentum enclosed by perichaetial leaves of sterile flowers below fruiting branches; flowers mostly solitary, with antheridial leaves scarcely differentiated, containing 2 or 3 antheridia 0.4 mm. long, with few paraphyses: fertile plants in compact, pale-yellowish to dullgreen cushions, with branching stems up to 5 cm. or rarely 10 cm. or more high, bearing crowded, erect-spreading, sometimes secund leaves: stem-leaves 4-11 mm. long, from an ovate base narrowed to a subtubulose point of variable length with an acute, minutely denticulate, incurved apex; costa in cross-section near the base showing mostly 6 layers of large, empty cells enclosing a median row of small, quadrate chlorocysts, usually 2 layers of large cells extending across the chlorocysts in the middle of the costa on the upper side and 1 layer on the lower side; hyaline blade of the lower part of the leaf about 5 cells wide on either side: seta dark-red, about 1.5 cm. long: capsule nodding, usually distinctly strumose, strongly curved and furrowed when dry, without stomata; annulus none; peristometeeth divided to below the middle into slender papillose forks, the articulations below close, vertically striate; lid with a slender beak about the -length of the capsule: spores slightly rough, up to 16 fx in diameter.
Type locality: Europe.
Distribution: Newfoundland to Minnesota, and southward to Florida and Louisiana; Bermuda; also throughout Europe.

Leucobryum glaucum, commonly known as leucobryum moss or pin cushion moss, is a species of haplolepideous mosses (Dicranidae) with a wide distribution in eastern North America and Europe.