IV. 



THE ANTHOCEROTES 



129 



arise is the inner of two cells formed by a transverse wall in a 

 surface cell. The outer cell (see Figure 67, B) divides almost 

 immediately by another wall parallel with the first, so that the 

 group of antheridia is separated by two layers of cells from 

 the surface of the thallus. The inner cell in A. Pearsoni at 

 once develops into an antheridium; but in most species the 

 cell divides first by a longitudinal wall into two, each of which 



Fig, 67. — Anthoceros Pearsoni. Development of the antheridium: A, apex of the 

 thallus, with very young antheridium, X about 500; B, <>. somewliat older stage; 

 C, still older stage, somewhat less highly magnified; D, an older, but still im- 

 mature antheridium, X about 200. 



generally divides again, so that there are four antheridium 

 mother cells, all, however, unmistakably the product of a single 

 cell, and if a comparison is to be made with the antheridium of 

 any other Liverwort, the antheridium in the latter is homol- 

 ogous, not with the single one of Anthoceros, but with the 

 whole group, plus the two-layered upper wall of the cavity in 

 which they lie. 



The first divisions in the antheridium are the same as those 

 in the original cell, i.e., the young antheridium is divided longi- 

 tudinally by two intersecting walls, and the separation of the 



