Manchester Meuioirs, Vol. liv. (1910), No. 11. 7 



in partially fused pairs. Two circumstances tend to 

 favour this view that the triangular steles have six 

 bundles, rather than three, as the earlier descriptions 

 stated. Firstly, there are really six distinct bundles in 

 some cases, though that is comparatively rare. Secondly, 

 the bundle, together with its carinal canal, is usually 

 tangentially elongated. This latter circumstance, as 

 already suggested, appears to me to be due to the fact 

 that each bundle is accompanied through a large part of 

 its course by a pair of sporangiophore-traces, one on either 

 side. The weight of evidence, however, appears to me 

 strongly in favour of the single nature of each bundle 

 in normal cases. Admittedly, most examples would 

 be so interpreted, apart from preconceived ideas ; but 

 the crucial sections are clearly those which are cut 

 above the level of the sporangiophores and below the 

 succeeding node. Such sections are not common, because 

 the nodal wood makes its appearance a very short distance 

 above the departure of the sporangiophore-trace Jn 

 several examples, however, the bundle is here seen to be 

 very definitely single. A very good example is seen 

 in Photo. I of the Plate (Manchr. Museum Coll. R. 801 A), 

 in which the tissues are completely preserved. This 

 section also illustrates the extreme delicacy of the vascular 

 tissues. Further evidence is afforded by many sections 

 in which the bundles are partially broken down. The 

 xylem mass is commonly detached from the medulla, and 

 more or less adherent to the cortex ; it is noteworthy 

 that in such cases the xylem invariably breaks away in a 

 single piece, and when this piece is attached to the cortex 

 it lies betiveeii the bases of the sporangiophores. A few 

 tracheids are commonly to be found separated from this 

 principal xylem mass on one or both sides ; these smaller 

 strands lie opposite the sporangiophores and must be 



