EXPLANATION OF THE FIGURES. 463 



FIG. 



10. Mother-cell with four spores. The membrane of the foriner is beginning 



to dissolve, x 300. 



11. Longitudinal section of ripe fruit, X 100. 



Figs. 12 15. Fissidens taxifolius. 



12. Young leaf seen from the surface, X 300. 



13 15. Cells of a somewhat more developed leaf of the same species, show- 

 ing different stages of development of the chlorophyll-granules, 

 X 400. 



PLATE XXIV. 



1. Germinating spore of Platy cerium alcicorne. The inner spore membrane 



has emerged from the ruptured exosporium in the form of a row of 

 three chlorophyll-bearing cells. The lowest of these cells has already 

 developed a capillary root. X 400. 



2. Young prothallium of Gymnogramma calomela nos, X 25. 



3. Young prothallium of Asplenium septentrionale, X 50. 



4. A shoot spontaneously detached from an old luxuriant prothallium of 



Gymnogramma calomelanos. It has developed a number of antheridia, 

 X 150. 



5. End of the shoot of an old prothatlium of the same species, x 2. 



Eigs. 6 12, Pteris serrulata. 



6. Eore-edge of a developed prothallium, x 150. 



7. Longitudinal section perpendicular to the surface, of a fully developed 



prothallium. The small papillae below are antheridia,' the longer ones 

 archegonia. X 75. 



8. Longitudinal section of a young antheridium, X 400. 



9. Apical aspect of the same. The course of the septa of the central cell is 



shown by dotted lines. X 400. 



10. Same view of a more developed antheridium, whose central cell is already 



divided into sixteen cells, x 400. 



11. Side view of an almost ripe antheridium, X 300. 



12. Same view of an empty antheridium, X 400. 



13,14,15. Spermatozoa of Asplenium septentrionale, killed with iodine. 13 is 

 X 1200, 14 and 15 are X 300. 13 and 14 are lateral views, and 15 is 

 seen from above. The mother-cell is still attached to the spermatozoon 

 in fig. 14. 



Figs. 16 19. Ceratopteris thalictrokles. 



16. Young prothallium with attached spore, and an antheridium, x 150. 

 17 19. Lateral views of young antheridia, X 300. 



