Dicranum Moss

Dicranum rhabdocarpum is an easily recognized species that occurs in the flora area only in the Rocky Mountains and the mountains of Arizona. It is the only species in the section Dicranum that has erect, straight to weakly arcuate capsules. Other important distinguishing features are the ovate-lanceolate, straight, obtusely acute, 1-stratose leaves with alar cells 1- or 2-stratose in part and the subpercurrent to percurrent costae that are smooth or weakly toothed on the abaxial surface near the leaf apex. Dicranum rhabdocarpum has been placed in the segregate genus Orthodicranum by J. M. Holzinger (1925b) and other bryologists mainly because of its straight and erect capsules. However, it differs from taxa commonly placed in that genus, i.e., D. flagellare, D. fulvum, D. montanum, D. strictum, and D. viride, by the elongate, pitted cells and the alar cells that are sometimes 2-stratose.

Plants in dense tufts, green to yellowish green or brownish, ± glossy. Stems 2-8 cm, tomentose with reddish brown rhizoids. Leaves straight or nearly so, spreading, little changed when dry, smooth, 3-5.5 × 0.6-1.2 mm, concave or tubulose proximally, tubulose to slightly keeled above; ovate-lanceolate, apex obtusely acute; margins serrate near apex; laminae 1-stratose; costa subpercurrent to percurrent, ¹/10-¹/8 the width of the leaves at base, smooth or weakly toothed on abaxial surface near apex, with a row of guide cells, two weak stereid bands, at least in basal part of leaf, adaxial and abaxial epidermal layers of cells not differentiated; cell walls between lamina cells not bulging; leaf cells smooth; alar cells 1- or 2-stratose in part, differentiated, not extending to costa; proximal laminal cells linear-rectangular, pitted, (45-)65-120(-150) × (13-)16-17(-19) µm; distal laminal cells shorter, narrow, pitted or with few pits, (20-)30-45(-60) × (5-)8-10(-13) µm. Sexual condition dioicous; male plants about as large as the female or slightly smaller; interior perichaetial leaves ± abruptly acuminate, convolute-sheathing. Seta 1.5-3 cm, solitary, rarely two per perichaetium, yellow to reddish brown. Capsule 1.5-4 mm, erect, straight or nearly so, furrowed when dry, brown; operculum 1.6-2.8 mm. Spores 13-19 µm.

Orthodicranum rhabdocarpum (Sullivant) Holzinger

Dicranum rhabdocarpum Still. Mem. Am
Acad. II. 4: 172. 1849.
Dicranum scoparioides Schimp.; Besch. Mem. Soc. Sci. Nat. Cherbourg 16; 164. 1872.
Dioicous: male plants in more or less separate tufts, more slender than the fertile, branching, with rather large flowers scattered along the stems, the antheridia about 0.6 » long: fertile plants in compact, pale glossy-green tufts, with stems 3-4 cm. long and leaves erect-spreading, the points irregularly flexuous or straight when dry, never crispate and rarely subsecund: stem-leaves about 5 mm. long, ovate-lanceolate, acute, serrulate on the margins about one fourth down; costa pale, vanishing below the apex, serrulate on the back above, just above its broadened base about 50 p, wide and one tenth the width of the blade or less, in cross-section near the middle showing about 4 guide-cells with stereid-bands above and below of about 2 rows of cells not always well differentiated; alar cells -golden -brown or hyaline, more or less inflated, not extending to the costa, the cells above elongate with unequally thickened walls pitted nearly to the apex, the median ones about 8 fx wide and 40-60 x long; inner perichaetial leaves narrowly costate, rather gradually narrowed to a nearly smooth, slender point scarcely one half the broader part in length: seta yellow or finally reddish, solitary, up to 2.25 cm. high: capsule erect, cylindric, 3-3.5 mm. long, furrowed when dry, with exothecal cells, except near the mouth, elongate with unevenly thickened slightly sinuous walls ; annulus wanting ; lid with its erect beak nearly two thirds the length of the capsule; peristome-teeth reddish-brown, vertically striate, divided or perforate often three fourths down, the inner articulations prominent : spores slightly rough, up to 1 8 fi in diameter.
Type locality:' Colorado.
Distribution: Colorado, New Mexico, and Mexico.