Leucobryum

Leucobryum is a genus of haplolepideous mosses (Dicranidae) in the family Leucobryaceae. The name comes from the Greek leukos, meaning white, and bryon, meaning moss.
Description.
Leucobryum species are in found in erect, dense, and often rounded cushions. Their color varies from white to grayish or bluish-green. Species are characterized by having thick, whitish leaves with a large, expanded costa. It has been suggested that the characteristic pale color exhibited by some species is caused by air bubbles in the leucocysts. The bubbles are theorized to be necessary for the function of the chlorocysts for the purpose of gas exchange.
Species are dioecious, with male plants stunted and found growing among the leaves of the female plants. Sporophytes are rare.
There are approximately 122 species of Leucobryum worldwide. Only two species are known to occur in North America.