Howe and Underwood: The Genus Riella 224 



19 and 20. Spores, outer and inner faces, X 305- 



Figures 4, 18-20, are drawn from material collected by Schott in 1855 ; the others 

 from material collected by Earle and Tracy, April, 1902. 



I'l.AlF. 12 



Figs. 21 and 22, Kiclla Aincricaiia Howe & Underw. ; Figs. 23-36, Kiclla afj'niis 

 Howe & Underw. 



21. Germ plant, X 245. 



22. Same in edgewise view, X245. 



23. Gametophyte of AV<7/(/ ^^;/«, X II- 



24. Apical portion of another, with involucres and antheridial locuU, /^ 11. 

 25 and 26. Involucres, X ^^• 



27 and 28. Spores, outer and inner faces, respectively, X ZIP- 



29 and 30. Germinating spores, X 55- 



31. Germ plant, showing the earlier cell divisions, X 245. 



32-36. Various forms assumed by the germ plants, X 55- The principal vegeta- 

 tive point is indicated by c. The elongate form represented in Fig. 36 is common 

 when the young plants are well covered with water. 



