THE BRYOLOGIST 
Vol. XXI March, 1918 No. 2 
MOSSES AS ROCK BUILDERS 1 
W. H. Emig 
The history of the travertine now to be found in the Arbuckle Mountains 
of the south-central part of Oklahoma begins with the removal of the Cretaceous 
strata from the underlying Paleozoic rocks during the Pleistocene age; a cycle 
of erosion that reduced the ancient mountains to a plateau radially dissected 
by short streams with small flood plains, rapids, and waterfalls. Some of these 
waterfalls were altered by the accumulations of the recent deposits of soft lime- 
stone — travertine — to such an extent that the falls attained a maximum height 
of 60 to 100 feet, and a width of 100 yards to nearly a half mile. The physio- 
graphic factors that have influenced the growth of these recent deposits have 
been aided in their work, to a considerable extent, by the presence of certain 
water plants, especially the tufted growths of the mosses Didymodon tophaceus 
(Brid.) Jur. and Philonotis calcarea Sch. 
The dense tufts of Didymodon are more commonly distributed along the 
moist ledges extending across the shallow streams. From an examination of 
the various travertine ledges, plants of Didymodon evidently had a greater share 
in the building of this kind of rock than the plants of Philonotis. A third species 
of water moss, Octodiceras Julianum Brid., was also found in small quantities 
in three different locations. The long branched moss stems fixed the tangled 
masses of algae, Oedogonium and Vaucheria, to the rock surfaces of the rapids 
or cascades. These little mats of plants bend with the undulating surface 
of the running water and apparently stretch like rubber. The water evap- 
orates from the more exposed plant surfaces; carbon dioxide gas diffuses into 
the air; the minerals held in solution concentrates in the plant mass; while 
calcium carbonate slowly, crystallizes about the filaments in a manner very 
much like the formation of crystals about strings that are suspended in a satur- 
ated solution of cane sugar. The young plants at the surface of the water 
continue to grow, but the incased filaments gradually decay, leaving behind 
small calcareous tubules arranged like a mass of coarse fiber. 
The incrustations about plants of the water moss Didymodon are more evident 
than those formed about algae or the mosses Octodiceras and Philonotis. The 
dense moss tufts, projecting one to four inches above the surface of the water 
at the margin of waterfalls, are always saturated like a sponge. As the water 
evaporates from the leaves and stems, most of the free carbon dioxide escapes 
1 Contribution from the Department of Botany, University of Pittsburgh. 
The January number of the Bryologist was published March is, 1918. 
