464 EXPLANATION OF THE FIGURES. 



PLATE XXV. 



FIG. 



1. Aspidium filix-mas. Longitudinal section of a young archcgonium in 



process of formation, X 200. 



2. Gymnogramma calomelanos. Similar section of a slightly more developed 



antheridium, x 400. 



3. Pleris serrulata. Archegonium soon after the formation of the germinal 



vesicle, x 400. 



4. An archegonium of the same fern without the axile cellular row of the neck, 



at the same stage of development, x 400. 



5. Aspidium filix-mas. Longitudinal section of a similarly developed arche- 



gonium, x 200. 



6. Gymnogramma calomelanos. Transverse section of the neck of an arche- 



gonium at the same stage of development, X 200. 



7. Further developed archegonium of the same fern shortly before the burst- 



ing of the apex, in longitudinal section, x 400. 



8. Pleris serrulata. A similarly developed archegonium, X 400. 



9. Central cell of an archegonium of the same fern, it has been grazed by a 



longitudinal section, and the germinal vesicle thereby injured, so that it 

 exhibits folds of the membrane, x 500. 



10. Central cell of an archegonium of the same fern seen from above. Tiie 



microscope bas been focussed to the upper surface of the cell of one of 

 the first archegonia of a young prothallium, whose parenchymatal 

 cushion was still thin, and permitted the passage of much light, x 400. 



11. Pleris serrulata. Portion of a longitudinal section of a prothallium with 



two archegonia ; one with the apex just burst, the other nearly ready 

 to burst, x 400. 



PLATE XXVI. 



1. Gymnogramma calomelanos. End of a shoot of a prothallium, x 5. 



2. Gymnogramma clirysophylla. Abnormal archegonium, from a longitudinal 



section of an old luxuriant prothallium, x 200. 



3. Gymnogramma calomelanos. Portion of a longitudinal section of an old 



luxuriant prothallium, which has a knob-like excrescence, x 50. 

 3*. Cortical layer and some of the cells of the inner tissue filled with a mass 

 of mucilage and oil of the above knob, X 300. 



Figs. 4 20. Aspidium filix-mas. 



4. Archegonium at the moment of impregnation. In the central cell of the 



archegonium which has been grazed by two longitudinal sections are 

 three spermatoza still in motion. The inner mouth of the canal of the 

 neck has already become closed again by the expansion of the surround- 

 ing cells, x 300. 



5. Longitudinal section of an archegonium shortly after impregnation. The 



enlarged impregnated germinal vesicle does not yet quite fill the central 

 cell, x 300. J f 



