V THE ANTHOCEROTEAL 123 



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 does not at 

 once develop into an antheridium, at least in most species, 

 although in the case of a doubtful species, probably A. Vincen- 

 tiamis from New Zealand, Leitgeb ^ found normally but one 

 antheridium in each cavity. The cell divides first by a longi- 

 tudinal wall into two, each of which generally divides again, so 

 that there are four antheridium mother cells, all, however, unmis- 

 takably 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 homologous, 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 stalk 

 from the upper part is secondary ; indeed in the earliest stages 

 it is difficult to tell whether these longitudinal divisions will result 

 in four separate antheridia or are the first division walls in a 

 single one. Secondary antheridia arise later by budding from 

 the base of the older ones, so that in the more advanced con- 

 ditions the antheridial group consists of a varying number, in 

 very different stages of development (Fig. 58). After the first 

 transverse walls by which the stalk is separated, the next 

 division in each of the upper cells is parallel to it, so that the 

 body of the antheridium is composed of nearly equal octant 

 cells. Then by a periclinal wall each of these eight cells is 

 divided into an inner and an outer cell, and the eight central 

 ones then give rise to the sperm cells, and the outer ones to 

 the wall. The four stalk cells by repeated transverse divisions 

 form the four-rowed stalk found in the ripe antheridium. The 

 uppermost tier of the stalk has its cells also divided by vertical 

 walls and forms the basal part of the antheridium wall. The 

 transverse and vertical division walls in the central cells alter- 

 nate with great regularity, so that there is little displacement 

 of the cells, and up to the time of the separation of the sperm 

 cells the four primary divisions are still plainly discernible, and 

 the individual sperm cells are cubical in form. In the peri- 

 pheral cells hardly less regularity is observable. Except near 



1 Leitgeb (7), vol. v. p. 17. 



