180 EDWAED C. JEFFREY ON 



trace oi'iginated and i;ouse([uently the Ijranch would lie in the axil of the leaf, which is not 

 the case. 



If the cause he sought of all the manifold contradictions, which, assuming the 

 correctness of the writer's course of argument, are present in the figures and statements 

 cited above, it is to be found in the fact, that the figures in (question are inverted, in 

 other words, in the fact, that, contrary to what is the case in Equisetum, the branches 

 of the Calamites are represented as originating above the nodes, and by inverting 

 the figures above mentioned all the difficulties which have been described at once 

 disappear. It may be further stated, that it is only possible for the branches to 

 uniformly alternate with tlie leaf-traces, whether the arrangement of the strands at 

 the nodes is continuous or alternating, wlien the former originate between the strands 

 which run up to the nodes, since it is from these same strands that the leaf-traces 

 are derived both in Calamites and Equisetn. 



But if the conclusions of the last paragraph be accepted as correct, Williamson's 

 areas of macerated parenchyma no longer lie below the node, and consequently cannot 

 be used as an explanation of the tubercles occurring below the nodal constrictions of 

 calamitean medullary casts. 



At this point the following quotation from Renault [op. clt., p. 89) may be intro- 

 duced apropos of photograph 1 (Pi. 28, lig. 1), copied from his monograph {op. clt., 

 atlas, pi. 47, fig. 7). 



"Les lames de tissu fondamental qui scparent les coins ligneux s'elargissent a leur 

 partie snperieure o planche 47 fig. 7, 8 (ces deux figures doivent etre vues retournees) 

 et forment une sorte de gouttie'"e ou de canal allant de la moelle Ti la peripheric; en 

 coupe transversale ces organes out une section elliptique ; il n'est pas rare de trouver 

 une cavite dans la region centrale, produite par la disparition, de celkiles polyedriques 

 qui forment une sorte de moelle (M. Williamson les a designes sous le nom de infrano- 

 clal canals): les cellules qui coniposent la couche peripherique sont allongees dans 

 le sens radial, prismatiques, polygonales sur une coupe transversale et rectangulaires 

 sur une section faite suivant leur largeur, leurs parois portent des ornements ponc- 

 tues; il est assez frequent de voir des tracheides se detacher des coins ligneux, 

 penetrer au milieu de ce tissu particulier et se confiDudi-e avec lui, leur nondjre est egal 

 a celui des lames de tissu fondamental secondaire qui separent les coins ligneux. Les 

 racines adventives, quand elles se developpaient, etaient en rapport avec ces organes, 

 que nous considerons comme des organes particuliers expectants, que nous distingue- 

 rons sous le nom d'organes rhiziferes.'' 



The three important features of this citation are, that Renault states that his 

 figure, which is reproduced in our j)hotograph 1 (PI. 28, fig. 1) , should be inverted. 



