354 



SPHENOPHYLLEAE. 



Schenk particularly and van Tieghem. I can find no grounds for this 

 union with Salvinia, which is opposed to all that we know of the 

 fructifications. The heterospory which is employed to defend it is 

 more than doubtful, and a comparison with the rudimentary central strand 

 of that aquatic plant would be a bold step, even if there was a re- 

 semblance between them ; but no such resemblance has been disclosed by 

 Janczewski's careful examination of the bundle in Salvinia. On the other 

 hand, as it seems to me, the primary structure precludes all thought 

 of Calamariae and Equisetae. There therefore remains only the series of 

 Lycopodeae, in which we may perhaps find some points of connection. 

 But here too much good-will is needed and various presuppositions. 

 Assuming for instance that the primary central bundle belongs to the 

 concentric type, then it may no doubt be compared with the axile strand 

 of Lycopodiae. But this is as yet only an assumption ; the bundle might 

 just as well be a triarch radial strand, and then there would be no 

 resemblance to the structure of the stalk in any living plant. Schenk : 

 endeavours to prove that the verticillate position of the leaves, which does 

 indeed often occur in Lycopodium, is an unimportant difference, but he has 

 overlooked the remarkable superposition of these whorls, which must 

 however be an important element in the question and requires much 

 consideration. To these peculiarities in Sphenophyllae must be added 

 the structure of the secondary wood, which has no analogue either in 

 living or in any known fossil plants. It is not so much the appearance 

 of this formation, as its absolutely peculiar character, which must make 

 us hesitate, and all the more because, as has been already said, the com- 

 parison of the external characters and of the primary structure with those 

 of Lycopodieae rests on very weak foundations. To compare the secondary 

 wood of Sphenophyllum with that of Sigillaria, as van Tieghem proposes, 

 is to my mind simply impossible. It will be best therefore to renounce 

 for the present all forced attempts at classification and to regard the group 

 as sui generis, as standing by itself and independent. I myself incline 

 to the view that it is only from the discovery of fresh specimens further 

 back in the series of deposits that we can hope to find such a place for 

 Sphenophylleae in the system as will be fruitful of further results ; but it 

 must be confessed that the prospect of such discoveries is at present un- 

 fortunately very small. 



1 Schenk (10), vol. ii. 



