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A TEXTBOOK OF THEORETICAL BOTANY 



archegonia, we may assume that cross-fertilization between different prothalli 

 is the general rule. 



The antheridium develops from a single superficial cell of the prothallus 

 (Fig. 485). By successive oblique divisions a central cell is isolated, surrounded 



Fig. 485. — Dryopteris filix-mas. 

 Diagram showing the succes- 

 sion of cell divisions in the 

 formation of an antheridium. 

 {After Strasburger.) 



by a number of peripheral cells which contain the chloroplasts of the original 

 cell. The first division wall is funnel-shaped, with the wide end upwards. 

 This is followed by a dome-shaped wall across the top of the funnel, thus 

 enclosing a central cell. The upper cell then divides by a ring-shaped wall. 



Stalk cell 



Wall 



Antherozoids 



Cell 



Fig. 486. — Dryopteris filix-t?ias. Mature 

 antheridium on the surface of the 

 prothallus. 



The antheridium thus consists of two ring cells, one above the other, a discoid 

 cap cell and the central cell. 



The divisions of the central cell are irregular in number, but about thirty- 

 two cells are usually formed, called antherozoid mother cells, and from 

 these the antherozoids are developed (Fig. 486). Each nucleus is trans- 



