The Carboniferous Arborescent Lepidodendra. 53 



sections, C.N. 422 to 426, cut successively from the same 

 branch. In the lowest of this series, we find the commence- 

 ment of an equal dichotomy, whilst in the uppermost one 

 this dichotomy is far advanced towards its completion. 

 Three of the above sections are represented in Memoir XVI., 

 Plate 8, Figs. 23, 24 and 25, including the dichotomy seen 

 in the latter section. 



Thus far I have done little more than lay before palaeo- 

 botanical students a series of carefully observed facts, the 

 greater number of which have not hitherto been published, 

 and even those which have already been recorded in my 

 various Memoirs are now laid before my readers in a col- 

 lective and arranged form for the first time. We have next 

 to consider what bearing these facts have upon the contro- 

 versy which has led to the publication of this Memoir. 

 When my earlier Memoirs were published, I was under the 

 impression that the branches of Lepidodendroid trees grew 

 like ordinary living exogens ; and that what were originally 

 young twigs became enlarged as they grew older, under the 

 influence of additional agencies associated with advancing 

 years. All the facts of organization, so far as they went, 

 were accurately stated even in my Memoir XVI. (1889) 

 Meanwhile the sections in my collection continued to increase 

 rapidly, throwing additional light upon the true history of 

 these objects. Some of these novelties were described and 

 illustrated in Memoir XIX. (1892), but even then I was 

 much more occupied with questions of morphology and 

 histology than of development. Yet, later, my close 

 association with my distinguished friend and colleague 

 Dr. D. Scott, brought developmental questions to the front. 

 I was still under my old impressions respecting the modes 

 of growth of these Lepidodendroid trees. 



My prolonged investigation made it increasingly evident 

 that the largest number of the leaves, leaf-traces, and 



