Black: The imbedded antheridium in Dryopteris 571 



12-24. Nepkr odium ntoJle. 



12. A structure, similar to a young archegonium, which may be the beginning of 

 an imbedded antheridium. 



13. An older stage. This could represent a stage in the formation of an imbedded 

 antheridium. 



14. A five-celled, deep-seated structure similar to a step in the development oP 

 imbedded antheridia. The densely granular cytoplasm and large resting nuclei are 

 indicated. 



15. Imbedded antheridium, projecting slightly. Cells beginning to round up, 



16. Small imbedded antheridium, with almost mature sperms, adjacent to a super- 

 ficial one. 



17. An antheridium of deep-seated origin, projecting half way above the surface 

 of the prothallium, 



18. Two cells under a cover-cell a of a deep-seated four-celled structure. This, 

 and the following figures are from consecutive sections of a prothallium, 



19. The same two cells of structure a are seen. Three cells in the cover of 

 structure b project slightly from the surface. 



20. More cells ol the cover of structure a are seen. The lower cell of the first 

 pair is below this cover. In structure b there are two cells, one projecting up into 

 the cover, 



21. The beginning of the third structure c is indicated here by three small cells, 

 part of the cover. Two cells of structure b show. In structure a the second pair 

 of cells, with the wall dividing them at right angles to the wall dividing the first pair 



fig- iQf ^j is seen. 



22. The cells of three structures appear as one contiguous mass of actively 



growing cells. Both nuclei of the second pair of cells of structure a are present. 

 In structure b three cells in addition to those already described are seen beneath them. 

 The cover of structure c projects considerably above the surface. Only three cells of 

 this last structure show. 



23. Structure a presents about the same appearance as in the preceding figures. 

 Two cells of structure b are visible. This section passing through the neck-like pro- 

 jection of structure c discloses two small cells in it. Beneath this are four cells. 



24. The two lowest cells of structure c are seen to resemble strikingly an ^g^~ 

 and ventral canal-cell. Above this so-called ventral canal-cell, three cells appear, two 

 of which were present in fig. 23, c. Structure c consists, then, of nine cells, running 

 through figs. 21-24. The cells in these three structures differ from the surrounding 

 cells in their granular contents and large nuclei. 



