460 EXPLANATION OF THE FIGURES. 



FIG. 



19. Racomitrium ericoides. Fragment of a lateral branch of a pro-embryo 



with the attached germ-plant, x 300. 



20, 21. Fissidens bryoides. Longitudinal sections of archegonia, fig. 20 ready 



for impregnation, fig. 21 just impregnated, x 300. 



22. Young fruit-rudiment of Bryum argenteum detached, x 300. 

 22*. The same turned round 90, X 300. 



23. Longitudinal section of the vaginula, and of a fragment of the seta, and 



the adjoining parts of the shoot of the same species, x 25. 



PLATE XX. 



PHASCUM CUSPIDATUM. 



1. Longitudinal section of a rudiment of an archegonium, x 400. 



2. Similar section of a young archegonium, x 400. 



3. Upper end of the same, x 600. 



4. Longitudinal section of an archegonium, whose apical cell has ceased to 



multiply, X 250. 



5. Longitudinal section of an archegonium shortly before the rupture of the 



apex, x 500. 



G. Archegonium whose apex has lately burst, in longitudinal section. The 

 still globular daughter-cell within the central cell only fills a small por- 

 tion of the latter, x 250. 



7. Accidental transverse section of the place of junction of the neck, and the 



ventral portions of an archegonium, x 250. 



8. Central cell of the ventral portion of an archegonium which has been 



cut longitudinally, in the state of development shown in fig. 6, x 500. 



9. Archegonium just impregnated, X 400. 



10. Longitudinal sections of the lower part of the neck, and of the upper part 



of the ventral portion, of an archegonium, with a two-celled fruit- 

 rudiment uninjured by the section, X 300. 



11. Similar section of an archegonium with a four-celled fruit-rudiment, 



X 200. 



11*. A fruit-rudiment, detached, X 400. 



ll c . Perspective view of the course of the cell walls of the same. 



12". A four-celled fruit-rudiment, detached, X 400. 



12*. The same turned round 90. 



13. Longitudinal sections of an impregnated and abortive archegonium. 



X 300. 



14. Similar section of a detached fruit-rudiment, x 200. 



15. Similar section of a fruit-rudiment with the growing calyptra and vaginula, 



X 75. 



15*. Outside of the apex of the same fruit-rudiment, x 400. 



16. Portion of the contents of an almost ripe antheridium. Each of the poly- 



gonal cellules of the interior of the organ encloses the mother-cell of a 

 spermatozoon, x 600. 



