142 



MOSSES AND FERNS 



CHAP. 



develops directly into the capsule instead of the latter being 

 determined by the second transverse walls. In the next 

 youngest stages found (Fig. 71, B) the archesporium was 

 already differentiated. A comparison of this with the corre- 

 sponding stage of Anthoceros shows conclusively that the two 

 are practically identical in structure. The columella, evidently 

 formed as in Anthoceros, and as there made up of four rows of 

 cells, is surrounded by the archesporium cut off from the peri- 



FlG. 69. — N otothy las orbicularis {^\)W.). Development of the archegonium, x6oo; x, the apical cell. 



pheral cells. Leitgeb's surmise that the columella is a second- 

 ary formation is, therefore, for N. orbicularis at least, entirely 

 erroneous, and it is extremely likely that when normal speci- 

 mens of the other species are examined from microtome 

 sections, in the young stages at least, a similar columella will 

 be found. The single embryo that Leitgeb ^ figures of N. 

 orbicularis (valvata) is at once seen to be abnormal, and as his 

 conclusions were drawn from a study of similar dead embryos 

 1 Leitgeb (7), vol. v. PI. IV. Fig. 77. 



