— 140 — 



forms which remained arborescent replaced the compound rays 

 by a system of smaller multiseriate rays with its more uniform 

 distribution of ray parenchyma. The typical ray structure of the 

 more recent Dicotyledons accordingly appears to be the multi- 

 seriate conditions". 



In a paper 'The origin and dispersal of Herbaceous Angio- 

 sperms" (1914), E.W. Sinnott and J.W. Bailey deal with the origin of 

 the herbaceous plants. On several points they do not seem to agree 

 with the view quoted above, yet in the main they insist on the 

 continuous cylinder as a starting point. They contest that the rays 

 around the leaf traces in the herbs should have been transformed 

 into interfascicular parenchyma. "Jeffrey and his school have main- 

 tained that the herbaceous stem was derived from the woody type 

 by a conversion into parenchyma of whole segments of the central 

 cylinder directly opposite the bundles which were to depart as 

 leaf-traces, and that these segments constitute the interfascicular 

 parenchyma between the bundles of the herbaceous stem". They 

 report that in fact primary xylem is always found on the inner 

 side of the interfascicular segments in the herbaceous plants. 

 They admit that the chief factor in the evolution of the her- 

 baceous structure of the stem has been a decrease of the acti- 

 vity of the cambium. They are also sceptical of the hypothesis 

 concerning the localization of the primary wood into smaller groups 

 caused by a herbaceous tendency, in view of the fact that distinct 

 bundles are present in many families, where herbaceous forms are 

 not found. In their opinion the isolated bundles are differentiated 

 by an increase in the breadth of the rays. 



They compare the herbaceous structure of the stem with 

 that of the first annual ring of the wood, which standpoint seems 

 to be quite unassailable. On the whole they do not seem to share 

 the American view entirely. 



After this very short resumé of these interesting papers I 

 shall give my own view on this question. 



In the American considerations it seems to me that an appre- 

 hension of the vascular bundle as a special organ is lacking. The 

 authors are speaking of protohadrom, but not about protoleptom. 

 Yet these tissues are connected and found together, forming iso- 

 lated vascular bundles in plants of high phylogenetic age. The 

 protostele in the Ferns is no doubt a vascular bundle similar to 

 other vascular bundles in the stem of these plants. The connection 



