EXPLANATION OF THE FIGURES. 445 



FIG. 

 5*. The cast-off calyptra (consisting of the ruptured portion of the tissue of 

 the stem, which covered the cavity, together with the mucilage which 

 filled the latter), seen from below, x 100. 

 5". Some of the cells of the edge of this calyptra, x 300. 



PLATE III. 



1. Columella and right-hand longitudinal moiety of the lower part of a young 



fruit, the place at which the separation of the grand-mother-cells from 

 the surrounding tissue commences, X 250. 



2. Transverse section (high up) of a young fruit, x 100. 



3. Spore-mother-cells, just detached, x 250. 



4. 5 and 5*. Spore-mother-cells during the formation of the two secondary 



nuclei, x 250. 

 6. A similar cell after the formation. 



7 and 8. The same cells during the dissolution of these nuclei. 

 9. Spore-mother-cell after the formation of the four tertiary nuclei, x 250. 



10. The same shortly before the commencement of division, showing the begin- 



ning of the swelling of the cell-membrane. 



11. Spore-mother-cell (after the dissolution of the primary nucleus) in alcohol 



and water, which makes the cell-membrane swell, x 750. 



12. Spore-mother-cell at the commencement of division, examined in alcohol, 



X 750. 



13. A similar preparation after treatment with water, which makes the cell- 



membrane swell, x 750. 



14. Spore-mother-cell in alcohol before the termination of the division. The 



course of the edges of the septa which do not yet reach the middle 

 point of the cell upon the inner side of the cell-membrane is shown in 

 the drawing, x 750. 



15. An abnormal spore-mother-cell, x 250. 



16. Longitudinal section, perpendicular to the surface, of the end of a shoot 



which bears a group of rudimentary antheridia, x 300. 



17. Optical longitudinal section of two young antheridia, x 150. 



18. Optical transverse section of one of these antheridia, x 150. 



19. 20. Optical longitudinal section of more-developed antheridia, x 300. 



21. Longitudinal section of an almost ripe antheridium, x 300. 



22. Two mother-cells of spermatozoa, each containing a spermatozoon, x 500. 



PLATE IV. 



PELLIA EPIPHYLLA. 



1. Longitudinal section of a ripe spore, x 300. 



2. Sketch of a ripe spore in which the outlines of the cells only are shown, 



