Flora of North America species comparison

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Bryum argenteum

silver bryum, silver-moss, silvergreen bryum moss, silvery thread moss
Habit Plants gregarious or in dense mats, white-green to silver-green.
Stems

0.2–1 cm, strongly rounded julaceous or sometimes gemmiform.
Leaves

erect when moist, ovate to ovate-lanceolate, somewhat concave, 0.3–1(–1.2) mm;

base green;

margins rarely recurved proximally or plane distally;

apex broadly rounded to acute, not cucullate, hyaline in distal 1/4–1/2 of leaf or rarely nearly entirely green;

costa not reaching apex, apiculus present, sometimes short or nearly absent, hyaline, irregularly incurved when dry;

proximal laminal cells quadrate or short-rectangular, 12–18 µm wide, 1–2:1;

distal cells short- or elongate-hexagonal, (30–)40–80 × 10–15 µm, (1–)3–5:1, walls thin or somewhat thickened, not distinctly incrassate.
Seta

brown to red-brown, 1–2 cm.
Capsule

red to red-brown, ovate, 2–3 mm;

hypophysis differentiated, somewhat thickened.
Spores

8–15 µm.
Specialized

asexual reproduction by leaf axil bulbils, leafy, small.

Bryum argenteum
Distribution
from USDA
Nearly worldwide
[WildflowerSearch map]
Discussion

Varieties ca. 30 (3 in the flora).

Bryum argenteum is perhaps the most widespread and distinctive moss in the world, although in many regions it is found primarily in urban or other heavily disturbed sites and is mostly absent from native undisturbed habitats in the tropics. There are about 15 silver-white species described, with species definitions based on a combination of one of three or four different basic gametophyte morphologies combined with subtle differences in the sporophytes. However, much of the gametophyte variability in the complex is also exhibited by B. argenteum itself, thus confusing species-level identifications. This complex is urgently in need of worldwide molecular and morphological studies.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Stems loosely julaceous; plants green; leaves hyaline near apex; costal apiculus long.
var. majus
1. Stems distinctly julaceous or gemmiform to short-julaceous; plants hoary white to silver-green; leaves hyaline in distal 1/4 -1/2; costal apiculus absent, short, or long
→ 2
2. Stems 0.5-1 cm, julaceous; leaves longer than broad; distal laminal cells elongate, 3-4(-5):1; costal apiculus long.
var. argenteum
2. Stems shorter than 0.2 cm, sometimes gemmiform; leaves often broader than long; distal laminal cells short, (1-)2-3:1; costal apiculus absent or very short.
var. muticum
Source FNA vol. 28, p. 126.
Parent taxa Bryaceae > Bryum
Sibling taxa
B. blindii, B. calobryoides, B. chryseum, B. lanatum, B. oblongum, B. veronense
Subordinate taxa
B. argenteum var. argenteum, B. argenteum var. majus, B. argenteum var. muticum
Name authority Hedwig: Sp. Musc. Frond., 181. (1801)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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