Black : The imbedded antheridium in Dryopteris 561 



cases, a thickness twice as great as that of the normally grown 

 prothallium; the apical sinus consisted oi a large number of 

 apical cells as seen in the consecutive sections of a prothalHum. 

 The wings were correspondingly large and somewhat wavy- 

 margined. The entire prothallium, not having its period of func- 

 tioning and usefulness ended by the production of a sporophyte, 

 appeared overgrown in all directions. Archegonia and antheridia 

 were produced on the upper as well as the lower surface. It is in 

 the actively growing portion of the prothallium, /. ^., the vicinity 

 of the apical sinus that one would look for some manifestation of 

 apogamy. Well up in this region of the prothallium a structure 

 w^as seen in a position to suggest an apogamous embryo, but 

 this proved to be an imbedded antheridium {figure 7). Normal, 

 as well as one or more imbedded, antheridia were found on the 

 same prothallium. The initial cell of an imbedded antheridium is 

 not distinguished in any way from the initial cell of an archegonium. 

 The first wall laid down in the development of an archegonium is 

 a periclinal one cutting off the initial cell of the neck. In a deep- 

 seated antheridium the first division is likewise periclinal. The 

 outer or superficial cell forms the cover, while the inner cell gives 

 rise to the spermatogenous tissue. In all cases thus far observed, 

 the second division of the inner cell of such an antheridium is an 

 oblique one {figure 7). The resulting cells in this instance were 

 unequal. In other cases, the division, also oblique, resulted in 

 more nearly equal cells, as in figure 2. The nuclei in these cells 

 were large, the cytoplasm dense and granular, and in staining 

 characteristics typical of cells in young archegonia or antheridia. 

 Three almost equal cells are seen in a developing antheridium in 

 figure ^. Further divisions now take place in three planes until 

 the structure becomes quite massive {figtires 4.-7). In figures 5 

 and 6^ the identity of the structure is shown in its shrinking away 

 from the surrounding cells. The proximity of these developing 

 imbedded antheridia to the apical region is seen m figures 7, 2, -^,5, 

 and 6, In figure 7 is pictured the most typical form of a deep- 

 seated antheridium. This is globular, projecting slightly above 

 the surface of the prothallium." As the antheridium nears maturity 

 the tendency to bulge outward is more pronounced. In the earliest 

 stages the antheridium is usually even with the surface of the pro- 



