PTERIDOPHYTES 



167 



a single layer of cells; while the inner cell develops 100-200 or more 

 sperm mother cells. 



Polypodiaceae. — In the Polypodiaceae the antheridium is derived 

 ■from the outer cell following the periclinal division, as in the case of the 

 leptosporangiate sporangium. In this cell there 

 appears first the funnel wall, which cuts off the 

 basal ring cell; then the dome wall appears, 

 intersecting the funnel wall and outlining the 

 central cell ; and finally the cap or cover cell is 

 cut out of the dome cell, completing the ring 

 cell (fig. 392). These divisions result in three 

 peripheral cells investing a central one, the 

 former producing the wall of the antheridium, 

 the latter the sperm mother cells, usually thirty- 

 two in number (sometimes sixty-four). There is 

 thus a decrease in the output of sperms in passing 

 from Marattiaceae to Polypodiaceae, just as in 

 the case of the spores, but it is much less ex- 

 tensive. The sperm is large and spirally coiled, 

 consisting of a large body (chiefly nucleus) and 

 a conspicuous cytoplasmic beak, from which 

 forty to fifty long retrorse cilia arise. 



Archegonium. — The archegonia appear late 

 in the history of the gametophyte, being de- 

 veloped on the ventral side in the region of the 



apical notch (fig. 391). Their development is anthe'ridia; in the upper^ 



very uniform, and follows the usual course most antheridium on the 



' .J , . -n ■ V 1 11 ii, right side the funnel and 



among ptendophytes. By a penchnal wall the . „ , j 



of f J J f dome walls have appeared ; 



superficial initial is divided into the primary in the three other com- 

 neck cell and the inner cell ; and by another P'^te antheridia the cover 

 transverse division the latter becomes the central ! .. ^, ^pp^^"'" ; ^""^ 



pletmg the three peripheral 



cell and the basal cell (fig. 393, a). This row of cells; the central cell has 

 three cells — primary neck cell, central cell, and developed sperm mother 

 basal cell — is perhaps the most commonly ob- 

 served stage in the development. The primary neck cell produces a 

 neck of three or four tiers (fig. 393, b-d), with four cells in each tier. 

 The central cell produces the axial row, the first division resulting in 

 the primary neck canal cell and the primary ventral cell. Among the 

 Marattiaceae the primary neck canal cell produces two neck canal cells; 



Fig. 392. — Young gam- 

 etophyte of fern bearing 



