2 On the Fossil Plants of the Coal-Measures. [Nov. 15, 



M. Renault, in 1885, expressed the opinion that the fossils origin- 

 ally described by Dr. Williamson under the name of Astromyelon* in 

 which the structure is well-preserved, were the roots of Arthropitus 

 (our Calamites) and Calamodendron. He has now found conclusive 

 proof of the truth of this hypothesis, and in his latest workt he 

 gives numerous figures of roots, with Astromyelon structure, arising as 

 appendages on the stems of Catamites, Bornia, and Calamodendron. 



It therefore became necessary to reinvestigate our English 

 specimens of Astromyelon Williamsonis (from which the French 

 fossils are said to be specifically distinct) in order to ascertain their 

 true nature. 



A specimen in the Williamson collection shows clearly three ap- 

 pendages with the typical structure of Astromyelon, arising from a 

 main axis which shows structural features characteristic of a 

 Calamitean stem. M. Renault's conclusion may, therefore, safely be 

 extended to the English specimens. 



The structure of the fossils hitherto known as Astromyelon William- 

 sonis has been examined in detail, with a view to determining their 

 morphological nature. It is found that they present, in all respects, 

 the characteristics of roots, so far as these can be recognised in fossil 

 plants. 



In the larger specimens, such as have been found in direct con- 

 nection with the stem of Calamites, there is a well-marked medulla, 

 which is surrounded by a ring of primary xylem-strands, varying in 

 number, from twenty-five downwards. The development of each 

 xylem-strand was centripetal, for the spiral tracheides lie at the 

 external angle of each strand. 



In well-preserved specimens, at an early stage of development, the 

 primary phloem can be recognised, alternating with the primary 

 strands of wood. These anatomical features are characteristic of the 

 roots of all vascular plants. 



The secondary wood, which has been observed at all stages of de- 

 velopment, agrees in structure with that of the stem of Calamites. 

 In favourable cases the cambium can be seen, and secondary phloem 

 has also been found. 



The mode of branching is shown to be endogenous. 



There is some evidence that these organs had a double endodermis, 

 ;as is the case in tne roots of the recent Equiseta. 



At the exterior of the cortex (which always had a lacunar zone) a 

 protective epidermoidal layer was formed, probably arising from the 



See Williamson, " Organisation of Fossil Plants of Coal -Measures, Parts IX 

 -and XII," 'Phil. Trans.,' 1878 and 1883; Eenault, "Genre Astromyelon," 

 4 Ann. des Sci. Geologiques,' vol. 17, 1885, and ' Mem. de la Soc. des Sci. Nat. do 

 Sa6ne et Loire,' 1885. 



t ' Flore Fossile d'Autun,' &c. Part 2. 1893. 



