— 27 — 
Falls, Plate XVI, fig. 2, the calcareous deposits are 60 feet thick immediately 
above the natural fall, but as they extend upstream for a distance of 150 yards, 
they gradually diminish to only a few feet in thickness. At one time travertine 
covered completely the present Turner Falls, which are about one-eighth their 
former size. During the last extensive erosion cycle, the unwashfed formation 
on either side of the main channel was unaltered, but as the soft portions of the 
rocks crumbled away, the channel became deeper, the fissures in the travertine 
opened and were extended into a deep gorge. In spite of successive erosions, 
the travertine continues to grow by the aid of algae and mosses. The mosses 
act only indirectly in the precipitation of calcium carbonate, principally by 
supplying a larger absorptive and adsorptive surface for the evaporation of the 
calcareous water. 
EXPLANATION OF PLATE XV 
Didymodon tophaceus (Brid.) Jur. X X 
1. Recent travertine showing the mode of travertine formation about moss plants that grow 
in erect tufts. 
2. Longitudinal section of hardened travertine showing the petrified moss plants. 
3. Cross-section of hardened travertine showing the minute canals left by the decay of the 
moss stems. 
4. Recent travertine showing the mode of travertine formation on pendent moss plants. 
5. Recent travertine formed by mosses and unicellular algae. 
6. The type of travertine that develops on pendent plants of Didymodon. 
University of Pittsburgh, Pittsburgh, Pa. 
MOSSES FROM FLORIDA COLLECTED BY SEVERIN RAPP 
Elizabeth G. Britton 
The last collection sent to us by Mr. Severin Rapp from the vicinity of 
Sanford, Florida, contains some very interesting species, including one tropical 
genus, new to the United States, Jagerinopsis Broth., and the extension north- 
ward of one tropical Dicranella determined by Mr. Williams as D . subinclinata 
Lorentz, heretofore known only from Cuba, Mexico and Panama to South 
America. This station in Florida and one of our own collections from the Isle 
of Pines, Cuba, are additions to its range as given in N. A. Flora. It grows 
“on clay banks along creeks” and may be looked for in the same habitats as 
its more common relative, D. L' Herminieri ( D . leptotrichoides R. & C.). D. 
heteromalla orthocarpa also has been found, but is rare in Florida, and Mnium 
cuspidatum seems to reach its southern range in this state. Excellent speci- 
mens of such common species as the following were also collected: Bruchia 
Donellii and B. Ravenellii , Trematodon longicollis, Leucobryum albidum (Brid.) 
Lindb. (L. sediforme), Syrrhopodon floridanus, Weisia longiseta , Funaria flavi- 
cans, three Southern varieties of Physcomitrium turbinatum, two Ephemerums, 
and Brachymenium Wrightii (Sull.) Broth., all in excellent fruit. Several 
Archidiums — A. alter nifolium, (sent as A. Ravenellii and A. tenerrimum ) and A. 
Donellii — show that this genus varies in Florida as much as other northern 
species do in that moist warm climate. 
