2 HOLDEN, Ahnonnal Spike of Ophioglossum vnlgatuni. 



Many of the features of the Ophioglossales are, 

 however, essentially peculiar to themselves, perhaps the 

 most marked being the division of the, usually, single 

 leaf into a well-defined sterile and fertile lobe or segment. 



Chrysler has recently revived the view, originally 

 put forward by Roeper, that the fertile spike represents 

 two fused, fertile, basal pinnae of a pinnate leaf, and 

 considers them derived by a further elaboration of the type 

 of fertile pinna characterising Aneiinia. The anatomical 

 evidence upon which he bases his adherence to this view, 

 appears, moreover, to be extremely convincing and is 

 decidedly stronger than any points so far urged against it. 



If Chrysler's view is to be regarded as correct, it 

 would appear that the members of the genus OpJiio- 

 gloss7i7ii are derived through a simple-leaved ancestor, from 

 the pinnate-leaved common ancestor of the group, and 

 that they represent a reduction series culminating in 

 Ophioglossum siuiplex. Ophioglosstiin palniatiim, on this 

 view, must be regarded as showing secondary specialisation 

 after the assumption of undivided leaf structure. 



The production of a branched fertile spike, as Bower 

 points out, appears to be intimately connected with the 

 lobing of the frond, and indeed from the figures given by 

 that author (" Origin of a Land Flora," p. 440, figs. c-g). 

 there is little in the external appearance, apart from the 

 greater projection of the sporangia, to distinguish his 

 BotrycJiiiivi simplex forma simplicissima, from a small 

 specimen of Ophioglossum. 



This projection of the sporangia in Botrychimn does 

 not appear to be a feature of primary importance, since, 

 according to Goebel, it has arisen owing to the pressure 

 exerted upon the sporangial cells by the cells of the axis 

 lying immediately beneath them. 



