2«2 



MOSSES AND FERNS 



CHAP. 



cells of which the archegonium is now composed are similar, 

 and the nuclei large and distinct. The cover cell next divides 

 into four by transverse walls (Fig. 146, E), and from these, as in 

 Marattia, the four rows of cells of the neck are formed. The 

 number in each row is four in the mature archegonium. The 

 ventral canal cell, which like that of Marattia extends the 

 whole breadth of the central cell, is separated almost simul- 



FiG. lifi.— Isoetes echinospora var. Brait7iiiiji\yc.'). Development of the archegonium, X 500 ; o, the 

 egg ; V, ventral canal cell ; h, neck canal cell ; D shows a two-celled embryo within the arche- 

 gonium. 



taneously with the appearance of the first transverse divisions 

 in the neck cells. The neck canal cell has at first a single 

 nucleus, which later divides, but there is no division wall 

 formed. Although the number of cells in each row of the 

 neck is usually greater than in Marattia, the neck canal cell 

 is shorter and extends but little between the neck cells (Fig. 

 148, B). 



The ^^% is very large, round or oval in form, and the 



