Stephenson. — Young Stages of Dicksonia and Cyathea. 3 



The sperms take some time to mature, and during this time 

 the wall is not easily permeable. The wall seems to be chemically 

 altered for a time, so that the nearly mature sperms may not 

 be injured if the prothallium is suddenly wetted. 



The sperms are ejected rather flatly coiled, and as soon as 

 the pellicle is softened in the water they spring out of it as 

 if they were in a state of great tension. This movement is very 

 jerky, especially at first. After half an hour they swim more 

 regularly, and straighten out more as death approaches. 



The " ring wall " in Cyathea is peculiar in that it is attached 

 to the peripheral wall. Docs this give us a suggestion as to 

 how the ring wall originated from a form as in Osmunda ? 



Osmunda. 



Cyathea. 



Campbell (" Messes and Ferns") considers that the antheridia 

 are intermediate between the Polypodiaecce and the Hymeno- 

 ■phyllacece. 



Archegonia. 



The archegonia, £s Campbell states, are simply those of the 

 Polypodiacece. It was found that the chief variations were in 

 the basal cell and the ventral-canal cell. A single basal cell 

 was nearly always present ; there were rarely two (fig. 12), 

 and rarely the cell seemed to be absent. 



The ventral-canal cell was cut off from the apex of the central 

 cell. Rarely it seemed to be due to the primary neck cell. 



In young prothallia forming the first few archegonia the 

 divisions of the segments at the apex do show some regularity. 

 The basal segment mav become the archegonium - rudiment 

 (fig. 21a). 



r 



Archegonia may be formed at a distance behind the apex. 

 The first wall is parallel to the surface of the 

 thallus — separating the " cover " cell, which 

 immediately divides by a vertical wall parallel 

 to the long axis of the thallus, and soon a wall 

 at right angles to this follows. 



View of Coveb 

 ell from above 



