VIII MARATTIALES 301 



Ophioglossum beyond question shows the simplest type of 

 sporangium of any of the Pteridophytes, and may be directly 

 compared to a form like Anthoccros. In both cases the arche- 

 sporium is hypodermal in origin, and is formed without any 

 elevation of the tissue to form separate sporangia. In Antho- 

 ceros, alternating with the sporogenous cells, are sterile cells 

 which divide the archesporium into irregular chambers contain- 

 ing the spores. A direct comparison may be drawn between 

 this and the origin of the archesporium in Ophioglossum, 

 especially in connection with Prof. Bower's discovery of a con- 

 tinuous band of sporangiogenic tissue in the latter. In some 

 species of Ophioglossum, too, the epidermis of the sporangium 

 has stomata as in Anthoccros. A comparison of these remark- 

 able points of similarity in the structure of the sporophyll of 

 Ophioglossum and the sporogonium of Anthoccros, together 

 with the very simple tissues of the former, led the writer 

 (Campbell (7) ) to express the belief that Ophioglossum, of all 

 living Pteridophytes, seemed to be the nearest to the Bryo- 

 phytes. Subsequent study of the eusporangiate Ferns has 

 strengthened that belief, and from a comparison of these with 

 Ophioglossum on the one hand and the Anthocerotes on the 

 other, it seems extremely likely that the latter represents more 

 nearly than any other group of living plants the form from 

 which the Pteridophytes have sprung, and that in the series of 

 the Filicinese at any rate, Ophioglossum comes nearest to the 

 ancestral type. Of course the possibility of Ophioglossum 

 being a reduced form must be borne in mind, and the sapro- 

 phytic habit of the prothallium may perhaps point to this ; still, 

 whatever may be its real character, there is little doubt that it 

 is the simplest of the Filicinese. The recent discovery of the 

 interesting O. simplex strengthens this view. 



The resemblances between Ophioglossum and the Antho- 

 cerotes are not confined to the sporophyte. The sexual organs 

 " — and this is true of all the eusporangiate Pteridophytes — show 

 some most striking similarities that are very significant. It 

 will be remembered that in the Anthocerotes alone among the 

 Bryophytes the sexual organs are completely submerged in the 

 thallus — the antheridia being actually endogenous. It will be 

 further remembered that in the eusporangiate Filicinese a 

 similar condition of things exists. 



