530 A TEXTBOOK OF THEORETICAL BOTANY 



of one of the Jungermanniaceae. It may eventually branch, and adventitious 

 budding is not uncommon, as in the Marattiaceae. 



Sexual development begins with the formation of antheridia, which appear 

 on the young prothalli before the archegonia. 



Fig. 528. — Osmunda regalis. Prothalli showing prolonged growth and 

 adventitious budding at base of B. C, Lower surface showing 

 rhizoids and position of archegonia. {After Goebel.) 



Development of the Antheridium 



The antheridia are borne marginally in young prothalli and also ventrally 

 on the wings in later stages. A single cell grows out beyond the general level 

 of the neighbouring cells, and its protruding apex is cut off by an oblique 

 wall. A second oblique wall, intersecting the first, cuts off a pyramidal 

 apical cell, which by further divisions may add to the lower cells first formed, 

 and builds up a short pedicel, which raises the antheridium still more above 

 the prothallus surface. The apical cell now divides transversely and cuts off 

 a wall cell at the top, from which other wall cells are produced, thus enclosing 

 the apical cell, which then divides to form antherozoid mother cells. The 

 whole antheridium is much larger than that in Dryopteris, producing more 

 than a hundred antherozoids. The wall is likewise formed of more cells 

 than is normal in the Leptosporangiatae, and it opens by throwing off a small 

 triangular opercular cell either at the apex or at the side, which resembles 

 the opercular dehiscence in the Eusporangiatae. The antherozoids are not 

 essentially different from those of Dryopteris. 



