GROUP II. BRYOPHYTA : HEPATIC^. 331 



B. The SPOROFHYTE. The early stages in the development of the 

 sporophj'te of the Anthocerotaceae appear to be much the same as in the 

 case of other Liverworts. The oospore divides transversely into an 

 epibasal and a hypobasal half : and each of these divides by two perpendi- 

 cular walls so that the embryo consists at this stage of eight cells. The 

 cells of the epibasal half divide transverse^ several times, and then 

 further apical growth in length is arrested by the formation of periclinal 

 walls, marking the differentiation of amphithecium and endothecium, first 

 in the four apical cells, and subsequently in those below them. By the 

 repeated formation of periclinal walls, the amphithecium comes to consist 

 of several layers of cells. The hypobasal cells undergo but few divisions, 

 giving rise to a bulbous foot, the superficial cells of which grow out into 

 papillae and penetrate between the cells of the adjacent tissue of the 

 gametophyte. 



As regards the differentiation of the epibasal portion of the embryo, in 

 Anthoceros (Fig. 197) the archesporium is developed from the innermost 

 layer of cells of the amphithecium, a peculiarity, the only other instance 

 of which, in the Muscinese, is to be found in the Sphagnaceae: the 

 endothecium gives rise to an axial strand of sterile tissue, termed the 

 columtlla, which is completely invested (except at the base, where it is 

 continuous with the tissue of the foot) by the archesporium. 



In all the genera some of the cells derived from the archesporium are 

 sterile. In some species of Anthoceros (e.g. vicentianus, giganteus, etc., 

 constituting the subgenus Anthocerites) these cells develope into elaters 

 with spiral thickening, each elater consisting of a row of cells with an 

 apparently continuous spiral band : in other species (e.g. tuberculatus, 

 glandulosus) the elaters have the same form, but they have no spiral band; 

 in others (Icevis, punctatus) the sterile cells do not form distinct elaters, but 

 a network of short cells, with spiral thickening, in the meshes of which 

 lie the mother-cells of the spores. 



The sporogonium of Anthoceros has no seta ; when the apical growth 

 has ceased, the capsule continues to elongate by basal growth, and hence 

 does not ever become fully mature throughout. The pod-shaped capsule 

 splits from the apex into two valves (Fig. 203). Stomata occur in the 

 epidermis of the capsule in most species of Anthoceros, but they appear to 

 be wanting in the other genera. 



Since the archegonia are sunk in the tissue of the shoot, the calyptra, 

 which invests the developing embryo, is developed mainly from the 

 surrounding tissue, and only to a small extent from the wall of the arche- 

 gonium. 



