36 GRIMMIACEAE 



often papillose, entirely lacking in Hedwigia; teeth entire, 

 cribose or cleft, often resembling those of Dicranum, but entirely 

 lacking the vertical striae characteristic of that genus. 



The Orthotrichaceae are usually included in this family, but 

 I entirely agree with Mr. Dixon that the differences in peristome 

 are fully sufficient to warrant the separation into two families. 

 Andreaea is the only genus likely to be misplaced in this family, 

 and when sterile one might easily have difficulty in distinguish- 

 ing it from the Grimmiaceae, but the plants are black even at 

 the top and much more slender than the great majority of the 

 Grimmiaceae. 



Key to the Genera 



i — Leaves ecostate Hedwigia 



Leaves costate 2 



2 — -Leaves crispate as in Ulota 4 



Leaves not crispate 3 



3 — Basal leaf cells linear, with incrassate sinuose walls; capsules all 



exserted Rhacomitrium 



Basal leaf cells but little longer than broad, walls not sinuose. . . .Grimmia 

 Basal leaf cells but little longer than broad, upper basal somewhat 

 sinuose; capsules immersed or emergent, not exserted. 



Grimmia Pennsylvanica and forms of G. apocarpa 



4 — Seta straight; upper leaves linear-lanceolate Ptychomitrium 



Seta arcuate (or sinuose when dry) ; upper leaves long-linear from a 

 short oblong base Campylostelium 



HEDWIGIA Ehrh. 



Lower part of the plants brown or black, the upper green, 

 with a tinge of gray due to the colorless tips of the leaves; cap- 

 sules entirely concealed in the longer, more slender perichaetial 

 leaves, the only indication of their presence being a slight en- 

 largement of the ends of some of the branches. The capsules 

 are almost spherical, with a clear-cut lid and no peristome; 

 they mature in spring. 



This genus is easily distinguished from all our other Grim- 

 miaceae and from the Orthotrichaceae by its ecostate leaves; its 

 large size, hyaline leaf apices and ciliate perichaetial leaves 

 prevent any confusion with the ecostate species of Andreaea. 

 By recent authors Hedwigia is put with the pleurocarpous 

 mosses, where it probably belongs. 



