XVII SUMMARY AND CONCLUSIONS 595 



evidence of a direct connection with either of the series of the 

 Hepaticse, and it is probable tliat the Anthocerotes should form 

 a class coordinate with all the other Liverworts on the one hand, 

 and the Mosses on the other. It is possible that the axial bun- 

 dle of sterile cells found in the capsule of Pcllia and Anctira 

 may be homologous with the columella of the Anthocerotes, 

 and the latter therefore to be considered as derived directlv from 

 some simple form among the anacrogynous Jungermanniaceae ; 

 but as the sporogonium in all the Anthocerotes that have been 

 thoroughly investigated shows absolutely the same type of 

 structure, and in no case a secondary formation of the columella, 

 this is hardly probable. In the higher Anthocerotes, also, the 

 w^all of the capsule, instead of simply serving for the protec- 

 tion of the spores, becomes a massive spongy green tissue com- 

 municating with the atmosphere by means of perfectly- 

 developed stomata of exactly the same type as those of the vas- 

 cular plants. This similarity in the assimilative system, 

 together with the basal growth of the sporophyte and the cen- 

 tral strand of conductive tissue, has of course suggested a rela- 

 tionship with the vascular plants. Indeed the sporogonium of 

 Anthoccros is much more like the spike of a small Ophioglos- 

 sum, for example, than it is like the sporogonium of Riccia. 



The Mosses, like the foliose Liverworts, seem to represent 

 a modern, extremely specialised type, with no direct connection 

 with higher forms. Probably related to the Anthocerotes 

 through Sphagnum, their further development has diverged 

 farther and farther away from the other Archegoniatse, until in 

 the Bryinese both gametophyte and sporophyte have little in 

 common with them. In both cases, an extreme specialisation 

 is attained which has no parallel among the Hepaticae ; but 

 whether it is the highly developed leafy gametophoric shoot of 

 Polytrichum or Daivsonia, or the equally complex sporogonium 

 of the same forms, the resulting structures are very different 

 from the corresponding ones in the vascular plants. 



The complete emancipation of the sporophyte is first 

 attained in the Pteridophytes. The development of a true root 

 at once establishes the independence of the sporophyte, and 

 inaugurates a new era in the history of the Plant Kingdom, as 

 there is at last developed a plant type, essentially terrestrial in 

 its habit. Throughout the Pteridophytes it is the sporophyte, 



