284 SCIENCE PROGRESS. 



development not found elsewhere, and resembles in a most 

 remarkable degree that of many thallose Liverworts. This 

 is especially the case with the sexual organs which are 

 much like those of Antkoceros, whose sporogonium has long 

 been recognised as the nearest in structure among the 

 Bryophytes to the Ferns. This resemblance of the 

 sporophyte in the two, is more than a general one. Not 

 only is the development of spores in Antkoceros subordinate 

 to the vegetative growth of the Sporophyte, but the origin 

 of the sporogenous tissue is directly comparable to that 

 in the eusporangiate Pteridophytes. In both cases the 

 sporogenous tissue (Archesporium) is derived from hypo- 

 dermal cells, and the segregation of the sporogenous cells 

 into definite sporangia is already indicated in the Antho- 

 cerotese, although the sterile cells do not form firm walls 

 between the masses of spores. Of the living Ferns, 

 Ophioglossum seems the nearest to Antkoceros so far as the 

 sporophyte is concerned. The sporangial spike of the 

 former may be directly compared to the upper part of the 

 sporogonium of Antkoceros, from which it differs mainly in 

 the complete separation of the archesporial cells, so that a 

 number of separate cavities are formed, constituting the large 

 sporangia of this genus. In some species, i.e., O. mdgatum, 

 the epidermis above the masses of spores develops stomata, 

 as in Antkoceros, and as in that form the sporogenous cells 

 are hypodermal and the outer wall of the sporangium at 

 first but a single layer of cells, which later becomes much 

 thicker. The sporangia project very little, and compared 

 with other Ferns are large. The genus Botrychmm 

 contains a number of species by which Ophioglossum is 

 connected with the Leptosporangiatce. There is a gradual 

 increase in the definiteness of the sporangium, which be- 

 comes more and more raised above the surface of the leaf 

 until in the more specialised forms, e.g., Botryckmm Vir- 

 ginianum, it is a globular capsule raised upon a short stalk. 

 As the sporangium becomes more distinctly separated 

 from the leaf, it becomes smaller, with a corresponding 

 increase in the number of individual sporangia. Thus 

 while in Opkioglossum the fertile leaf segment forms a 



