Black : The imbedded antheridjum in Dryopteris 567 



the meaning of the imbedded antheridium would be evident.- If 

 the migrating and fusing nuclei, producing the apogamous embryo 

 as described by Farmer and Digby, could be traced to such sexual 

 elements as might mature into a deep-seated antheridium or an 

 archegonium, the adaptation there would be more complete. The 

 morphological position of an imbedded antheridium, then, can be 

 regarded as only the expression of the potentialities of the plant, 

 one evidence of the response to environmental conditions. 



The sperms from either antheridium apparently differ in no 

 particular. There was a greater variation in the number of sperms 

 in the imbedded antheridia than in those of the normal type, the 

 imbedded antheridia being larger on the whole than the superficial 

 ones. The individuality of the deep-seated antheridium is shown 

 in its slight shrinkage from the surrounding cells. 



The case of the imbedded antheridium in which half consists 

 of mature sperms and the other half of three large cells, one re- 

 sembling very much an egg- cell {^figure lo), presents another 

 standpoint from w^hich these structures may be considered. This 

 is the subject as to the determination of sex. The question arises, 

 has any cell of a prothallium destined to be a sex-cell the po- 

 tentialities of either sex ? When w^e remember that these are 

 monoecious prothallia, that each cell came from a spore and that 

 all spores are alike, it would seem as if there were some basis for 

 such a supposition. If we accept this supposition as true, the 

 earliest stages o( the imbedded antheridium may be interpreted as 

 the earliest stages of an archegonium. After the first division of a 

 superficial cell into an inner and an outer cell, the inner cell instead 

 of developing into an archegonium becomes the initial of a deep- 

 seated antheridium. The origin of the case above cited may then 

 be explained as a sex-cell, the potentialities of either sex being 

 almost equal, so that half of the structure consists of sperms or 

 the male element, and the other half, composed of three cells, one 

 especially resembling an egg-cell, represents the female element. 



Another case, the lower antheridium m figure //, is shown where 

 more than one half of the structure consists of spqrm mother-cells, 

 the rest of the antheridium being taken up by a number of large cells, 

 which may represent the female element of the original cell. The 

 fact that maleness dominates in these structures and that imbedded 



