ISO MOSSES AND FERNS chap. 



this hypothetical type. Its sporogonium, however, simple as it 

 is, is more perfect than that of Riccia, and if our hypothesis 

 is correct, the Marchantiaceae must have been derived from 

 Sph(2rocarpus-\i\i& forms in which the sporophyte was still 

 simpler than that of existing species. Assuming that this is 

 correct, the further evolution of the Marchantiaceae is simple 

 enough, and the series of forms from the lowest to the highest 

 very complete. 



In the second series, the Jungermanniacese, starting with 

 SpJicerocarpiis, the line leads through Aneura, Pellia, and similar 

 simple thallose forms, to several types with more or less per- 

 fect leaves — i.e. Blasia, Fossoinbronia, Treubia, Haplomitriinn. 

 These do not constitute a single series, but have evidently 

 developed independently, and it is quite probable that the 

 typical foliose Jungermanniaceae are not all to be traced back 

 to common ancestors, but have originated at different points 

 from several anacrogynous prototypes. 



The systematic position of the Anthoceroteae is more ' 

 difficult to determine, and their connection with any other 

 existing forms known must be remote. While the structure of 

 the thallus and sporogonium in NototJiylas shows a not very 

 remote resemblance to the corresponding structures in SpJicsro- 

 carpus, it must be remembered that the- peculiar chloroplasts of 

 the Anthoceroteae, as well as the development of the sexual 

 organs, are peculiar to the group, and quite different from other 

 Liverworts.. To find chloroplasts of similar character, one must 

 go to the green Algs, where in many Confervaceae very similar 

 ones occur. It is quite conceivable that the peculiarities of the 

 sexual organs may be explained by supposing that those of 

 such a form as SpJicEvocarpus, for example, should become 

 coherent with the surrounding envelope at a very early stage, 

 and remain so until maturity. In Aneura we have seen that 

 the base of the archegonium is confluent with the thallus, in 

 which respect it offers an approach to the condition found in 

 the Anthoceroteae ; but that this is anything more than an 

 analogy is improbable. The origin of the endogenous anther- 

 idium must at present remain conjectural, but that it is 

 secondary rather than primary is extremely likely, as we know 

 that occasionally the antheridium may originate superficially. 

 In regard to the sporogonium, until further evidence is brought 

 forward to show that NototJiylas may have the columella absent 



