﻿192 



Howe : New American Hepaticae 



5. Lateral view toward apex of a thallus-segment, showing the numerous trich- 



omes, X 2 °- 



6. Marginal trichomes, X S3- 



7. Portions of thallus exhibiting the trichome -bearing elevations above the cap- 

 sules, X 2 °» * 



8-13. Outlines of transverse sections about 10 /x in thickness at selected points 

 from near the apex to the old and shriveled base, X 2 3- The trichomes do not ap- 

 pear so abundant as might be expected from the material used for microtome sectioning 



which may be explained by the thinness of the sections and by the fact that the de- 

 tached sections and fragments of the trichomes have not always adhered to the glass 

 slides. Fig. 8 shows small median scales. 



14. Epidermis and subjacent cells from a younger portion of the thallus, X 22 5» 

 The superficial layer is here represented as composed of collapsed cells. In the ex- 

 treme apical region only they are papilliform. 



15. Epidermis in older parts of the thallus, X 22 5- The collapse and disintegra- 

 tion of the cells of the outer layer is so complete that only a structureless cellulose film 



remains. 



16. Cross-section of thallus showing the cell structure and a young sporogonium, 



X5 



17. Spores, X 3°5- 



Figs. 1, 2, 4-7 and 17 from Hep. Am. no. 138 collected" in San Mateo County, Cali- 

 fornia, April, 1892, by Prof. D. H. Campbell; figs. 3 and 8-16 from material fixed 

 with I per cent, chromic acid and preserved in alcohol, collected by the author near 

 Berkeley, California, February 8, 1 896. 



