IX MARArriACE.E—ISOETACE/E 299 



also, and in ejeneral habit as well as the position of the 

 sporangia comes nearer the Icptosporangiatc Ferns. Of the 

 Ophioglossaceai, HelmintJiostacJiys on the whole approaches 

 nearest to the Marattiaceai, so far as the general character 

 of the sporophyte is concerned. The venation of the leaves 

 and dehiscence of the sporangia are very similar to Angtopteris, 

 and the green sterile tips to the sporangial branches hint at 

 a possible beginning of the lamina of the sporophylls in the 

 Marattiaceae. However, as the life-history of the plant and 

 its histology are almost unknown as yet, it is not possible to 

 draw any definite conclusion as to its affinities, and the question 

 whether the Marattiaceae are connected directly with the Ophio- 

 glossaceae, or have branched off from the same stock lower 

 down, must remain for the present unanswered ; but the 

 similarities in both sporophyte and gametophyte are too 

 numerous to make an entirely independent origin for the 

 two orders at all probable. 



In seeking a connection with the leptosporangiate Ferns 

 there are two points where this is possible. The higher 

 species of BotrycJiiuin show an unmistakable approach to 

 the leptosporangiate type. The archegonium neck projects 

 much more than in the other Eusporangiatae, and the vascular 

 bundles in the petiole are truly concentric. The venation of 

 the leaves also becomes that of the typical Ferns. The 

 sporangia are completely free here, and smaller and more 

 delicate, although truly eusporangiate in development. In all 

 these respects there is an approach to Osmunda, unquestionably 

 the lowest of the leptosporangiate series. HelnimtJiostacJiys 

 too may be almost as well compared to Osmunda as to 

 Angiopteris. 



On the other hand, in the circinate vernation of the leaf 

 as well as the histology, in the roots, and in the sporangia, 

 the Marattiaceae, especially Angiopteris, approach quite as 

 close or closer to the Osmundaceae than does Botrycliiuiu or 

 HelmintJiostacJiys. 



Isoetes differs so much from all other Pteridophytes that 

 it seems almost hopeless to try to assign it its proper position 

 in the series. The reasons for assigning it to the Filicineae 

 rather than the Lycopodineae, are first the character of the 

 gametophyte and sexual organs, and second the histology of 

 the mature sporophyte. The archegonium resembles very 



