Ferns and Mosses of the United States. 293 



tt Capsules without a Struma. 



12. D. scottianum. 13. D. undulatum. 



14. D. scoparium. 15. D. varium. 



36. D heteromailum. 17. D. xanthodon. 

 18. D. condensatum. 



XII. DiDYMODON. Hedw. 



a. Capsules inclined, 



1. D. purpureum. 2. D. inclinatum. 



b. Capsules erect, or nearly so. 



3. D. glaucescens. 4. D. rigidulum. 



5. D, trifanum. 6. D. capillaceum. 



7. D. paiiidum. 



XIII. Trichostomum. Hedw. 



1. T, lanuginosum. 2. T. canadense. 



3. T. microcarpon. 4. T. tenue. 



XIV. Splachnum. Linn. 



1. S. ampullaceum. 2. S. angustatum. 

 Several others, natives of Arctic America. 



XV. ToRTULA. Hedw. 



A. Leaves of the perichcetium convolute. 



1. T. convoluta. 



B. Leaves uniform. 



t Piliferous. 



2. T. muralis. 3. T. ruralis. 



tt Leaves mucronate. 

 a. Peristome tubidar beyond the middle. 



4. T. mucronifolia. 5. T. leucostema. 

 G. T. subulata. 



b. Teeth of the peristome almost entirely free. 

 7. T. unguiculata. 8. T. caespitosa. 



ttt Leaves awnless. 

 9. T.tortuosa. 10. T. fallax. 



11. T. humilis. 



