258 SCIENCE PROGRESS. 



our present knowledge we can see the great merits of this 

 memoir, though they were hardly appreciated at the time. 

 Conclusive proof is there given of the truth of the view of 

 Germar, Corda, and Dawes, that the ordinary form of pre- 

 servation of a Calamite is nothing but a cast of the medullary 

 cavity; the significance of the various markings on such casts 

 was rightly explained. The main lines of the anatomy of 

 both old and young stems were accurately laid down, and 

 the existence of true medullary rays in the secondary wood 

 demonstrated, while some evidence as to the mode of branch- 

 ing was already brought forward. This memoir undoubtedly 

 laid a sound foundation for our knowledge of the structure 

 of the Calamitean stem. 



Of the later memoirs the most important for the vegeta- 

 tive structure of Calamites is part ix. (1877), which contains 

 a splendid set of illustrations of the anatomy. A series of 

 very young stems are figured and described, and their re- 

 semblance at this early stage to stems of recent Equiseta is 

 recognised. This had become a point of great importance, 

 for the demonstration that the supposed stems, as shown in 

 ordinary sandstone specimens, were only casts of the hollow 

 pith, had to a great extent cut away the old grounds for 

 regarding the Calamites as Equisetaceous. Consequently 

 accurate anatomical evidence on this point was much needed. 

 The position and mode of attachment of the branches were 

 also very finely elucidated in this memoir, though of course 

 many important details were only made out at a later time. 

 In this paper the genus Astromyelon was founded, not having 

 been previously distinguished from Calamites. A later 

 memoir (part xii., 1882) was largely devoted to Asti'omyelon, 

 with which the smaller specimens, described by Hick and 

 Cash (38) under the name of My nop ky I hides, were identified. 

 It was not till a later time that we learnt the true nature of 

 Astromyelon, which, as Renault has conclusively proved, is 

 made up of the roots of Calamites and its near allies (39). 

 This result has since been amply confirmed by the study of 

 the English specimens. Although Williamson at the time 

 failed to detect this fact, he displayed great acumen in uniting 

 (and, as it has proved, quite correctly) forms so different as 



