GENERAL RESULTS— SPHENOPSIDA 623 



have taken place between the sterile and fertile lobes 

 in Calamostachys} The evidence, however, is as yet 

 insufficient to establish any such interpretation, and it 

 may well be that the Sphenophyllum analogy has been 

 pushed too far. There is no need to reduce every 

 sporangiophore to a leaf- lobe, for it is not at all 

 unlikely that in the Sphenopsida, as in the Pteropsida, 

 the spore - bearing organ may be sometimes a lobe 

 of a leaf, sometimes an entire leaf, especially as it is 

 often so difficult to distinguish between leaf-segments 

 and leaves in the vegetative region. 



Professor Bower regards the sporangiophore as " a 

 part sui generis as much as the sporangium is, and 

 not the result of modification of any other part." 2 

 Miss Benson, from a different point of view, has been 

 led to a similar conclusion. 8 There is much to be said 

 for this interpretation, which I provisionally adopted in 

 the First Edition of these " Studies" (p. 498). On the 

 actual evidence, however, there is nothing to prevent 

 our .regarding the sporangiophore as always of a foliar 

 nature, and it appears unadvisable to multiply cate- 

 gories of organs without necessity. The sporangium 

 and the sporangiophore are not really on the same 

 footing, for there must always have been distinct 

 organs of reproduction, whereas in innumerable cases 

 the organ which bears them is simply a leaf, or part of 

 a leaf. At the same time it is probable that the differ- 

 entiation of the sporangiophore took place very early, 



1 Scott, "Present Position of Palaeozoic Botany," Progressus Rei 

 Botanicae, Bd. i. p. 162, 1906. 



2 Origin of a Land Flora, p. 426. 



■' 3 "The Sporangiophore — a Unit of Structure in the Pteridophyta," 

 New Phytologist, vol. vii. 1908, p. 143. 



