THE GENUS EQUISETUM. 



181 



that the traces running in the medullary rajs are related to roots, and that they su e 

 equivalent to Williamson's intranodal canals. Renault gives no reasons for the 

 inversion, but obviously the figure, in its original position, is open to the same objec- 

 tions as have been urged in a former paragraph against the orientation of the similar 

 figures of Williamson and Scott. The observation that the organs, o, have a parenchy- 

 matous medulla which is surrounded by a zone of pitted cells comparable to the 

 peculiar tracheary elements of the basal node of the branches, or of the walls of the 

 rhizophorous pedicels of Equiseta is all the more interesting, because, as Renault 

 informs us, roots are actually attached to these organs. It is possible to accept his 

 first two statements, without admitting the accuracy of the third, viz., that the organs, 

 o, are the equivalents of Williamson's intranodal canals. If the reasoning of a former 

 paragraph is sound, the tracts of macerated parenchyma which Williamson called 

 intranodal canals are not really below the node at all but on the contrary above it, 

 consequently the organs described by Renault cannot be considered as their equivalents. 

 If Renault's figure, reproduced in photograph 1 (PI. 28, fig. 1), be compared with 

 photographs 5 and 6 (PI. 27, figs. 5, 6), it is not very difficult to decide that the 

 organs situated in the upper (really lower) medullary rays of the three figures are 

 equivalent, and since, if the course of reasoning adopted here is correct, these organs 

 in photographs 5 and 6 (PI. 27, figs. 5, 6) are branches they must similarly be branches, 

 or their homologues, in photograph 1 (PI. 28, fig. 1) . But Renault tells us, in the 

 passage quoted above, that in this case they are related to roots, and the inference 

 may be drawn, that they are the morphological equivalents of the rhizophoric buds of 

 Equiseta, which have an identical relation to the vascular strands and to the nodes. 



Renault (op. cit., texte, p. 92, 95, 107, 123) has not realized this, since both in his 

 figures and the subsequently published explanatory text he makes the traces of the ordi- 

 nary branches pass outwards above the leaf-traces and above the node, and not below the 

 leaf-traces and at the node, as must be the case if the mode of the argument previously 

 adopted by the writer is not fallacious. 



At the beginning of the discussion of the relation of calamitean branches to the node, 

 a figure from Weiss, our photograph 6 (PI. 30, fig. 6) , was cited, indicating, if the writer 

 has properly interpreted it, that externally at least the branches of the Calamites had the 

 same relation to the node as obtains in living Equiseta. A consideration of the internal 

 features has led, moreover, to a similar conclusion in regard to the position of the branches 

 in the ancestors of the Equisetaceae. In the case of the calamitean rhizophoric organs 

 on the other hand, first from the evidence of internal structural arrangements, the con- 

 clusion has been reached that they are the equivalents of branches and have the same 

 relation to the nodes, PI. 26, fig. 17, which is a copy from Weiss (Steinkohlen-Calamarien, 



