1 6 ANDREAEACEAE 



Family 2. ANDREAEACEAE. 



The only family of the order. Mosses of alpine or subalpine 

 habitat, growing upon granitic or slaty rocks; with the habit 

 and color of Grimmia. The appearance is always dark, some- 

 times black, and the leaves are very brittle and so dense 

 that they need to be soaked in a solution of caustic potash for 

 a few moments, in order to make their structure apparent under 

 the microscope. The presence of chlorophyll in the leaves is 

 not apparent except in very young leaves. Leaf cells small, 

 very thick walled. There is very little difference in the sporo- 

 phyte in the different species. 



ANDRE AE A Ehrh. 



Leaves without costa petrophila 



Leaves costate Rothii 



A. petrophila Ehrh. "Steep dry rocks and boulders near 

 Closter, N. J.," Muse. App. 42. '"On boulders near Sparta," 

 Geol. Survey N. J. Summer. 



A. Rothii W. & M. {A. rupestris of many authors.) "Rocks 

 by the Hudson River, Yonkers," Muse. App. 43 and E. C. 

 Howe, Bx! Summer. 



ORDER III. BRYALES 



Suborder I. Nematodonteae 



Peristome teeth solid, not transversely barred (very faintly so 

 in Buxbaumia), derived from several concentric series of cells of 

 the sporogonium. 



Family 3. GEORGIACEAE 



All of our mosses belonging to this family are distinct in the 

 four-parted peristome, each of the four teeth being composed of 

 a solid mass of cellular tissue. The leaves are ovate or lanceo- 

 late, smooth, costate, leaf-cells rounded-hexagonal. 



