452. 



MOSSES AND FERNS 



cells, which here are much longer than the others. It subse- 

 quently divides by a transverse wall, as may happen in the 

 Marattiacese and occasionally in Osmunda, but whether this 

 alvi^ays takes place is not certain (Fig. 263, A) . The four rows 

 of neck cells are all alike, and consist ordinarily of three cells 



Fig. 263. — A, Longitudinal section of nearly ripe archegonium, with two neck canal 

 cells ic, 1,^ Xs5o; B, section of an open archegonium, X27S; C, D, two cross- 

 sections of a young archegonium; L, the lobe at the base of which the arche- 

 gonium is formed, X550, 



each, the terminal ones being very long, and when the archego- 

 nium opens bending back strongly, but not becoming detached. 

 The central cell is surrounded by a single layer of tabular cells 

 cut off from the adjacent prothallium tissue, but these divisions 

 may extend to the lower neck cells (Fig. 263, A). The ^gg 

 is globular and shows no peculiarities of structure. Buchtien's 

 ((i), p. 24) account of the further development of the mer- 

 istem, as well as his figures, point to something very much like 

 a repeated dichotomy of the growing point ; a further investiga-i 



