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Leucobryum
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Leucobryum belongs to the family of mosses known as Leucobryaceae. This family is disputed among bryologists due to the similarity of costal modifications with Paraleucobryum, Brothera, and Campylopus and a peristome structure with Dicranum, a member of the family to which some bryologists claim Leucobryaceae should be included, the Dicranaceae. Andrews ( Bryologist 50:319-26, 1947) argued that the Leucobryaceae should be merged with the Dicranaceae. Brotherus (Crum & Anderson, 1981) recognized nine genera in the Leucobryaceae, all of them tropical except Leucobryum, which extends far northward into temperate latitudes and is also at home in the tropics of the Old and New world. There are approximately 122 species of Leucobryum world wide.

Leucobryum, generally means "white moss." Although, it is commonly called the pin cushion moss. The plants are in small to large, erect, dense, and often rounded cushions. Their color varies from white to grayish or bluish-green cushions. Robinson (Redfearn Jr.) suggests that the characteristic pale color of Leucobryum in large part is caused by air bubbles in the leucocysts, and the presence of air in the leaf is assumed to be characteristic of the Leucobryaceae. Furthermore, he concludes that "such bubbles are necessary for the function of the chlorocysts, which are remote from the surface of the leaf, and which could not properly exchange gases if the leucocysts were all filled with water." The stems are forked and the leaves are crowded, thick and fleshy. An interesting aspect of this moss is that it is dioecious, that is the male plants are dwarfed and are growing on or among the leaves of the female plants. The sporophytes of this moss, which are rare to find, have elongate, erect seta, and an asymmetric, 8-ribbed capsule which has 16 peristome teeth. The spherical spores are yellowish or brownish in color.

Of the 122 species worldwide, there are only 2 species that occur in Ohio, L. glaucum (Hedw.) Angstr. and L. albidum (Brid.) Lindb. The distinction of the two species is mainly based on size, and evidence to support the distinction came from a study of nuclear ribosomal DNA extracts. The study, done on a small population in North Carolina, demonstrated that there were two genetically distinct haplotypes that correlated to different size. Plants with leaf sizes under 5 mm were L. albidum species and the plants with leaf sizes of 5 mm or greater were of L. glaucum species (Patterson, et. al., 1998). L. glaucum has tall, compact cushions with stems 1 to 12.5 cm tall. The leaves are 3 to 9 mm in length. Asexual reproduction is by small clusters of caducous leaf-like gemmae at the stem tip and by leaves with rhizoids at the apex. This species occurs on humus, soil , rotting logs, tree bases, rock ledges in forests, swamps and bogs. Its range is Eastern to South central United States, the Caucasus, Japan, China and from Newfoundland to Manitoba in Canada. On the other hand, L. albidum has low, compact cushions with stems less than 1 cm tall, and leaves 2 to 4 mm long. Asexual reproduction is by small leaf-like gemmae on minute, forked branches at the stem tip and by caducous leaves with rhizoids at the leaf apex. This species occurs on moist humus, sandy soil, rotting logs (Pines especially), tree bases, hardwood trees, pines and palms, in forests, swamps and bogs. Its range is the Eastern United States, Mexico and Central America, and the Greater Antilles.

Bibliography

1. Ireland, Robert R. 1982. Moss Flora of Maritime Provinces. National Museum of Canada

2. Crum, Howard and Anderson, Lewis E. 1981. Mosses of Eastern North America. Columbia University Press

3. Redfearn Jr., Paul L. 1999. Bryophyte Flora of North America. Accessed 5/16/1999. Accessed at http://www.nybg.org/bsci/bfna/leucobry.html

4. Patterson, Bowles, Shaw, & Jonathan 1998. Nuclear ribosomal DNA variation in Leucobryum glaucum and L. albidum (Leucobryaceae): A preliminary investigation. Bryologist vol. 101 number 2 pg. 272-277.

Written by Jarrod Bonnick

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