EXPLANATION OF THE FIGURES. 445 



FIB. 



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. 

 38. 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. 



PELLTA 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. 



