IV. 



THE ANrilOCEROTES 



155 



that the divisions occur with a good deal of regularity. The 

 archesporial cells are divided by alternating vertical and trans- 

 verse walls into four layers of cells instead of two, as in Antho- 

 ceros, and these cells are arranged in regularly placed transverse 

 rows. At first the cells appear alike, but later there is a sei)ara- 

 tion into sporogenous and sterile cells as in Anthoccros. Mach 

 primary transverse row of cells becomes divided into two. The 

 upper row grows much faster, and its cells become swollen and 

 the cytoplasm more granular, while the lower row has its cells 

 remaining flattened and more transparent, i. c, there is a sep- 

 aration of the archesporium into alternate layers of sporogenr)us 

 and sterile cells as in Anthoceros, but here the 

 number of cells is double that in the latter, and 

 the longer axis of the cells is transverse instead 

 of vertical. In the portion of the archesporium 

 above the columella these alternate layers of 

 spore mother cells and sterile cells extend com- 

 pletely across, and Leitgeb has correctly fig- 

 ured this, although he probably was mistaken 

 in assuming that this arrangement extended to 

 the base of the capsule. 



The further development of the capsule is 

 much like that of Anthoceros, but the division 

 of the chloroplast takes place before the spore 

 mother cells are isolated, and the primary chlo- 

 roplast is evident almost as soon as the sporog- 

 enous cells are recognisable as such. The 

 cells of the columella do not become as elon- 

 gated as in Anthoceros, and develop thicken- 

 ings much like those of the sterile cells of the 

 archesporium; and it was this partly that led 

 Leitgeb to the conclusion that even where a 

 definite columella was present it probably arose 

 as a secondary formation in the archesporium, 

 similar to the formation of the axial bundle of 

 elaters in Pellia, and that in Notothylas as in 

 the Jungermanniales, the archesporium arose 

 from the inner of the cells formed by the first 

 periclinal w^alls, and not from the outer ones. That this is not 

 true for A'', oribictdaris is shown beyond question from sections 

 of both the older and younger sporogonium, and it would be 





Fig. 85. — Longitu- 

 dinal section of a 

 nearly ripe sporo- 

 gonium of N. or- 

 bicularis, Xso. 



