136 ARCHEGONIATES. 



as in the Pteridophyta and gymnosperms, is a transformation of the 

 entire contents of the cell, arid we may with much propriety regard the 

 spermatozoid of Chara and that of the fern as homologous structures. 

 But whether we are dealing with real homologies, or only with striking 

 analogies, is certainly a question concerning which there may be some 

 diversity of opinion. 



The fate of the spermatozoid of Chara after penetrating the egg and 

 the union of the two sexual nuclei is practically unknown in detail, and 

 a further discussion of the process of fecundation in the absence of more 

 facts would seem without value, since it is not the purpose to enter here 

 into any discussion of the homologies of the sexual organs of the 

 Characeas with those of the Archegoniates. 



THE EGG-CELL AND FECUNDATION. 



In more recent years the process of fecundation has been observed 

 in various genera of the Felicinex by Campbell, in Onoclea by Shaw, 

 and in Adiantum and Aspidium by Thorn. The author has followed 

 the process in Onoclea struthiopteris, and his observations confirm 

 those of Shaw, who has traced the behavior of the sexual nuclei in 

 great detail in Onoclea sensibilis, 



Soon after the division which cuts off the ventral canal-cell, and 

 before the archegonium of Onoclea struthiopteris is full grown, the 

 three central cells contain fine-meshed and densely granular cytoplasm. 

 Their nuclei are in the resting stage. The wall between egg and 

 ventral canal-cell is generally arched slightly downward into the egg- 

 cell. This wall is laid down in this position, at least in many cases, 

 and the concave upper surface of the egg does not seem to be due to 

 pressure from the ventral or neck canal-cell. 



As the archegonium matures it increases in size, and the cytoplasm 

 of the central cells becomes looser. A rather large vacuole has been 

 observed in the ventral canal-cell in the mature organ. It is well 

 known that in Onoclea the nucleus of the neck canal-cell often divides, 

 but a division of the cell does not follow, except, possibly, in rare 

 cases. The daughter-nuclei are reconstructed and lie usually close to 

 each other. The author has observed in several instances that the 

 division of the neck-canal nucleus took place at exactly the same time 

 as the division of the central cell which cuts off the ventral canal-cell. 

 Whether any special significance should be attached to this phenome- 

 non the author is unable to state. Observers have often been tempted 

 to consider the ventral canal-cell as a rudimentary egg, but if there be 

 good grounds for such a view it is, perhaps, as much in harmony 

 with the facts to regard the neck canal-cell or cells as aborted eggs. 



