I.EPIDODENDREAE. 2C>7 



surface of the scar when the preservation is imperfect. Ulodendron-stems 

 have occasionally been mistaken for stems of Megaphytum which have also 

 two lines of scars (see above on p. 167), as the literature testifies, but such 

 confusion is only possible where both the surface of the stem and the cups 

 are very badly preserved, and may be avoided in most cases by careful 

 examination of the specimens. 



Now comes the question, what were the organs which were inserted on 

 these scars. On this point a great variety of opinions finds expression in the 

 literature. Carruthers 1 , differing from all other authors, who look upon the 

 central circle only as the scar of separation of the lateral member and 

 explain the formation of the cup as the effect of the pressure of that member, 

 has tried to prove that the entire cup answers to the place of separation. He 

 considers the dot-like protuberances on its slope and the central scar also to 

 be vascular bundle-traces, and assumes the existence of strong adventitious 

 roots springing from these places. Apart from the fact that no trace of 

 such adventitious roots has ever been found, the anatomy of the organs is 

 most decidedly opposed to this view, as will be shown below. The idea of 

 a root with a mass of cortical bundles as well as the central strand must 

 seem to the botanist to be a priori open to objection ; and Kidston 2 has 

 supplied an excess of proof by describing and figuring a specimen in which 

 the slope of the cups is covered with quite normal cushions of the leaves of 

 Lepidodendron, and which is thus shown to be most certainly a segment of 

 the surface of the stem. There remains therefore only the possibility that 

 the scars in question bore vegetative branches or organs of fructification. 

 It is improbable that they bore vegetative branches, as Stur 3 has shown 

 against Geinitz 4 ; the great objection to this view is the regularity of the 

 planes of separation, for which 'no analogue can be found except in the 

 cladoptosis of our forest trees, the oak for example. That such separations 

 are at least not invariable is shown by the branching of Knorriae which 

 was described above, in which the pressure of the stumps that are left 

 causes the formation of lateral furrows on the main stem. Thus we come 

 back to the most natural and oldest idea, that these scars are the places of 

 separation of the fructifications. And here Stur has been led by a specula- 

 tion, which in my judgment IS quite unfounded, to a very remarkable result. 

 He sets out from the view that the surface of the stem is of exactly the 

 same character in Lepidodendron Veltheimianum and in Ulodendron 

 commutatum, and that the two must therefore be considered to be 

 identical forms. As he knows that there were cones of fructification 

 attached to the extremities of thin leafy terminal branches in Lepido- 

 dendron Veltheimianum, the scars on the thick stems could not possibly 

 have also borne cones. Vegetative branches are excluded for the reasons 



1 Carruthers (11). 2 Kidston (2), t. 4, f. 2. 3 Stur (5). * Geinitz (8). 



