No. 535] 



NOTES AND LITERATURE 



445 



among the fossil Lycopods is the fact that some of the great fos- 

 sil club-mosses, e. g., Lepidocarpon, bore unmistakable seeds. 

 This adds one more instance of the independent origin of seeds 

 in quite unrelated orders of Pteridophytes. 



It is among the ferns, however, that the interest of the paleo- 

 botanist has been especially centered, both in England and on 

 the continent. The abundance and perfection of the fern-like 

 fossils of the Paleozoic, especially those of the Carboniferous, 

 are sufficiently familiar, but a very large percentage of them are 

 merely impressions of sterile fronds. Numerous investigations 

 of these supposed fern-leaves have proved beyond question that 

 they are not ferns in the strict sense of the word, but are the 

 sterile leaves of fern-like plants which bore true seeds. It has 

 become apparent that these seed-bearing ferns, "Pterido- 

 sperms," formed a very important feature of the Carboniferous 

 flora, perhaps outnumbering the true ferns. Indeed, some en- 

 thusiastic students of these interesting plants have gone so far 

 as to doubt whether true ferns existed at all at this period!— 

 a conclusion with which it is needless to say few botanists would 

 be inclined to agree. True ferns must have preceded Pterido- 

 sperms, and it is hardly likely that none of them should have 

 left fossil remains, not to mention the fact that many of the 

 fossil fronds bear sporangia of whose true fern nature there can 

 be no reasonable doubt. 



Of the living ferns, the Marattiaceae are best represented 

 among the Paleozoic fossils, and their primitive nature is also 

 shown by a study of their structure and development. Most of 

 the Pteridosperms were probably derived from ferns of this 

 type, and it is in many cases apparently n<>t possible to decide 

 whether certain leaves bearing sporangia of the Marattiaceous 



of some Pteridosperms. It does not follow, however, as some 

 students of Pteridosperms have argued, that because the 

 sporangia of one doubtful Marattiaceous fern have been shown 

 to belong to a Pteridosperm, that therefore we must suspect all 

 of the sporangia of the Marattiaceous type. 



The geological history of the other living family of the euspo- 

 ningiate terns, the Ophioglossacea 1 . is extremely unsatisfactory. 



may perhaps be explained by the perishable nature of their 

 leaves. The soft leaves of Opkioglossum and Botrychium and 

 the absence of indurated cells from the sporangium would make 

 these plants very poorly fitted for preservation in a fossil state. 



