Cn. XXIV.] 



ASTEROPHYLLITES. 



473 



an internal pith answering in character to the Calamodendron, and 

 yet having outside of it another jointed cylinder vertically grooved 

 on its outer surface, so that in the same stem we have one calamite 

 enveloping another. Yet that they both formed part of the same 

 plant is proved by the following circumstances : — 1st. Near each 

 articulation of the pith radiating spokes are seen to proceed and 

 penetrate the ligneous zone. One complete whorl or circle of these 

 radii is visible in the foregoing fiorire near the bottom of the hollow 

 cavity, whilst another and superior whorl is incomplete; several radii, 

 corresponding to the first, remaining, while the rest have been broken 

 away, their place being shown by scars which they have left. 2 dry. 

 In addition to these whorls, called medullary by Professor William- 

 son, there are seen in other specimens a set of true or ordinary me- 

 dullary rays. 3dly. The woody zone, penetrated both by the spoke- 

 like vessels before mentioned and by the medullary rays, is usually 

 reduced to brown carbonaceous matter, preserving merely a tendency 

 to break in longitudinal slips, but in some specimens its fibrous tissue 

 is retained, and resembles that of Dadoxylon. 4thly. Outside of this 

 zone again is another cylinder, supposed to have been originally a 

 thick cellular bark, nearly equal to one-third of the whole stem in 

 diameter, grooved and jointed externally like the pith. 



In conclusion, I may remark that these discoveries make it more 

 and more doubtful to what family the greater number of Calamites 

 should be referred. Their internal organization, says Professor 

 Williamson, was very peculiar ; for while they exhibit remarkable 

 affinities with gymnospermous dicotyledons, the arrangement of their 

 tissues differs widely from that of all known forms of gymnosperms. 



Aster ophyllites. — The graceful plant represented in the annexed 

 figure is supposed by M. Brongniart to be a branch of the Calamo- 

 dendron, and he infers from its pith and medullary rays that it was 



Fig. 526. 



Asterophyllites foliosus. (Foss. Flo., 25.) Coal-measures, Newcastle. 



dicotyledonous. It appears to have been allied, by the nature of its 

 tissue, to the gymnogens, and to Sigillaria. But under the head of 



