OF THE WOODY ZONE IN CALAMITE. 177 



parenchymatous type seen in Mr. Binney^s plants. But 

 whilst on these points Mr. Butterworth^s specimens exhibit 

 so many features in common with Mr. Binney^s^ as in 

 mine^ the woody tracts are all provided with some medul- 

 lary rays. This structure identifies these specimens with 

 the Calamitea of linger, and makes it more probable 

 than before that a further study of Mr. Binney^s fine 

 examples will reveal medullary rays in them also. The 

 only absolute and permanent distinction that still appears 

 to separate my type of stem from the rest is the existence 

 of the verticillate medullary radii, which are equally absent 

 from all other described forms, but which alone I should 

 scarcely regard as constituting a sufficient basis for a 

 generic distinction. 



But, as I shall presently show, there are other circum- 

 stances which justify the provisional retention of my genus 

 Calamopitus. Mr. Butterworth^s specimens accord in a re- 

 markable degree with my description of the curious arched 

 deflection of the barred vessels from the surface of the 

 pith when passing the nodes, and also reveal traces of 

 vascular bundles passing from the interior to the exterior 

 of the woody zone at the same point, as indicated in my 

 fig. 17; but this arrangement is much less complicated 

 than in my examples. The vessels of each vascular tract 

 ascend in a compact form until they reach the node ; they 

 then divide right and left to be distributed to the two con- 

 tiguous vascular tracts above. Each bundle undergoes 

 no change in doing so, beyond bulging out somewhat to 

 admit of a large admixture of cells like those of the 

 cellular tracts, returning immediately to the former com- 

 pact arrangement as the diverging bundles enter their 

 respective vascular tracts in the joint above. The speci- 

 mens indicate that the exterior of the woody zone had 

 a furrowed Calamite-like outline, the external ridges 

 corresponding with the vascular tracts, whilst the de- 



SER. III. VOL. IV. N 



