452 



MOSSES AND FERNS 



CHAP. 



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

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

 Marattiaceae and occasionally in Osmunda, but whether this 

 always 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 (r, c XSSo; 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, XS50. 



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 ^^g 

 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- 



