,8,.. IS STIGMA RI A A ROOT OR A RHIZOME? 369 



each one to take an increased share in the work. Little by little, as 

 each new exogenous vascular zone was added to the entire exterior 

 of the secondary wood, which wood alone extended into the subterranean 

 structures, the upper margin of each pre-existing rootlet bundle 

 received an additional vessel or two, developed in a continuous line 

 from the periphery of the xylem zone, through the cortex, and 

 terminated on the rootlet bundle, between the pre-existing tracheids 

 and the phloem in contact with them. This continuous growth in 

 size, and in the number of the tracheids constituting this rootlet 

 bundle, is another of the many features of common occurrence 

 among these Carboniferous plants which are never met with in 

 any recent form. But these processes in no way make the rootlet 

 bundle other than a monarch ; and Mr. Hick himself admits that 

 *' If it could be shown that this bundle is really homologous with a 

 true monarch bundle, it would be a strong point in favour of the 

 root hypothesis." In this I agree with him. The root-bundles of 

 the ancient and the modern types are as homologous as the stem 

 structures of the two, i.e., so far as homologues can exist between 

 plants which, though belonging to the same great family, are, 

 nevertheless, in some respects so differently organised. 



I have dealt thus far with Mr. Hick's arguments because 

 they are but the superficial echoes of the ideas of M. Renault, 

 the high priest of the doctrines which I reject ; who, in calling 

 Stigmaria a rhizome, has constantly in view the angiospermous 

 structures so named, with which it has no kind of relationship. 

 M. Renault declares that Stigmaria, like the mint or the water-lily, 

 develops leaves and shoot-producing buds, as well as rootlets. I 

 deny as emphatically as ever that our British Stigmaria do anything 

 like this ; hence it neither is, nor can be, a rhizome in the sense in 

 which these writers use that term. But I have long had in mind 

 another much more complex aspect which these Stigmaria present, 

 and which has not yet received the attention that it demands. The 

 combined peculiarities presented by this remarkable organism seem 

 to me to demand a special and different nomenclature. In ray next 

 communication on the subject I hope to present these hitherto 

 undiscussed aspects in a definite form, whatever may be their true 

 value. 



W. C. Williamson. 



2B 



