iS8 MOSSES AND FERNS chap. 



sporogonium, however, simple as it is, is more perfect than 

 that of Riccia, and if our hypothesis is correct, the Marchanti- 

 ales must have been derived from Sphcerocarpus-\ike forms in 

 which the sporophyte was still simpler than that of existing 

 species. Assuming that this is correct, the further evolution 

 of the Marchantiales is simple enough, and the series of forms 

 from the lowest to the highest very complete. 



In the second series, the Jungermanniales, starting with 

 Spharocarpus, the line leads through Aneura, Pellia, and simi- 

 lar simple thallose forms, to several types with more or less 

 perfect leaves— ^.j^.^ Blasia, F ossombronia, Treubia, Haplomit- 

 rium. These do not constitute a single series, but have evi- 

 dently developed independently, and it is quite probable that 

 the typical foliose Jungermanniacese 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 Anthocerotes is more diffi- 

 cult to determine, and their connection with any other existing 

 forms known must be remote. While the structure of the thal- 

 lus and sporogonium in Notothylas shows a not very remote 

 resemblance to the corresponding structures in Spharocarpus, 

 it must be remembered that the peculiar chloroplasts of the 

 Anthocerotes, as well as the development of the sexual organs, 

 are peculiar to the group, and quite different from other Liver- 

 worts. To find chloroplasts of similar character, one must go 

 to the green Algae, 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 Sphmrocarpus, for example, should become co- 

 herent 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 An- 

 thocerotes; but that this is anything more than an analogy is 

 improbable. The origin of the endogenous antheridium must 

 at present remain conjectural, but that it is secondary rather 

 than primary is quite possible, as we know that occasionally the 

 antheridium may originate superficially. In regard to the 

 sporogonium, until further evidence is brought forward to 

 show that Notothylas may have the columella absent in the early 

 stages, it must be assumed that its structure in the Anthocerotes 



