RECENT WORK ON MOSSES AND FERNS. 37$ 



applicable to so many and varied organic forms, it is not to 

 be expected that all types could be covered by a simple 

 statement ; the separate lines of descent should be con- 

 sidered independently of one another, and so a general 

 opinion be gradually formed. As matters stand at present, 

 it may be concluded with reasonable probability that in certain 

 cases vegetative leaves have resulted from the sterile develop- 

 ment of sporophylls. But even if this were proved to 

 have been their constant and only mode of origin (and we 

 are far from being able to assert this) there would still 

 remain the question of the primary origin of the foliar 

 organs, as also of the root. On these points it must be 

 frankly admitted that we are still in the dark, though 

 their development and comparative study give some clues 

 upon which hypothesis may rest. 



We have thus briefly considered the two main points of 

 difference between Bryophyta and Pteridophyta. Little 

 has recently been gained as certain knowledge regarding 

 the increased complexity of form, but the recognition of 

 septation, as leading to a segregation of sporogenous 

 masses, introduces an important factor. Though it does 

 not in any sense solve the problem, this acceptance of an 

 idea of septation, coupled with the view that the Euspo- 

 rangiate Ferns were the more primitive, does appear to be a 

 step towards its solution. 



One direct result of Campbell's view of the Kusporan- 

 giate Ferns is, so to speak, to pollard the evolutionary tree. 

 In the past, attempts have been made to deduce the various 

 Pteridophyte types from Leptosporangiate Ferns, arranging 

 them in extended sequence ; this involved reduction on a 

 large scale, " elimination " of the identity of the sporangium 

 by fusion; the introduction of the idea of " sporocysts," 

 a term applied first to those deeply-sunk sporangia of 

 Ophioglossum which were believed to represent a fern 

 sorus. not a sporangium (Strasburger, Bdt. Zeit., 1873). 

 Such ideas of reference of the divers stocks to a single type 

 have long been either loosely held, or rejected ; but so long 

 as the Leptosporangiates are considered the most primitive, 

 there will always be a disposition to look, in other lines of 



