STIGMARIA. 



more strongly on this point, and made use of it, in conjunction with 

 fresh arguments, as the foundation of another view, namely, that the 

 axes were rhizomes and their appendages leaves. In this case the Sigil- 

 larieae and Lepidodendreae must, as he argues, be compared with the 

 rootless stock of Psilotum, though the leaves, which are present in Stig- 

 maria, are quite wanting on the rhizome-shoots of the other plant. This 

 view is very vigorously opposed by Williamson 1 . Putting aside the 

 occasional bifurcations and the puzzling scars in the angles, he appeals 

 more particularly to the anatomical structure, which he finds to be almost 

 identical with that of the rhizophores of Selaginella Martensii. The two 

 organisms are certainly like one another in appearance, and this might be 

 expected, since we have to do in the one case with the rare monarch 

 radial strand, in the other with a collateral bundle. It is only from the 

 position of the bast or cambium that the difference between them can be 

 determined. However, the resemblance does not go so far as might be 

 imagined from Williamson's 2 figure of the transverse section of Selaginella, 

 which is correctly drawn indeed, but wrongly explained. The large cells 

 opposite the initial group, which Williamson supposes to be the bast, are 

 really parts of the wood-strand, tracheides in the young state ; the real bast 

 is to be sought in the small-celled peripheral zone marked C. The bundle in 

 this case is late in reaching its ultimate development, and hence the mistake, 

 which is easy to understand. But it cannot be denied that Schimper's idea 

 entirely gets rid of most of the difficulties. There is first the fact that the 

 dichotomously branched axes develope their appendages in progressive suc- 

 cession. On the supposition of a branch-system consisting of similar members 

 (roots and lateral roots), this would imply a different structure and origin 

 for the members of the same generation. And this would certainly be 

 remarkable and without direct analogy in living vegetation, even supposing 

 the distinction between progressive and dichotomous branching to have lost 

 its importance to the same extent as at the present day. But if we consider 

 the Stigmariae to be leafy rhizomes, everything is as it should be. It has 

 been repeatedly observed before that the position of the appendages does 

 not agree with that of lateral roots, but that it does agree very well with 

 that of the leaves ; that they leave scars behind them of a definite shape 

 when they drop off. which never or at least only very rarely happens with 

 roots, is a point which Schimper regards as most important. The specimen 

 in my possession and described above on p. 268, which has the vegetative 

 points, may also really favour Schimper's view ; for there the young appen- 

 dages approach nearer to the apex than is ever the case with roots on 

 account of the root-cap, for which there is too little room left. There is, 



Williamson (1), xi, and (6). * Williamson (1), XI, p. 291, t. 53, f. 13. 



