CORDAITEAE. 109 



both in impressions and in the pebbles ; the leaves in these buds show the 

 convolute aestivation, such as may be seen in the beautiful drawing of a 

 transverse section given by Renault 1 . Where the inner structure can be 

 determined in branches evidently belonging to Cordaitae, the structure of the 

 wood is seen in all cases to be that of Araucaroxylon. We find too that 

 the wood has exactly the same character in the portions of branches which 

 are preserved in the pebbles of Grand' Croix, and which are remarkable for 

 the unusual breadth of the cylinder of pith. The tissue of the pith usually 

 disappears at an early period, persisting only in thin transverse diaphragm- 

 plates which show greater solidity, just as happens for example at the 

 present day in branches of the walnut-tree. In consequence of this 

 peculiar behaviour the branches of true Cordaitae are sharply differentiated 

 from other trees with a similar woody structure. Hence also Araucaroxylon 

 medullosum, Kr. (Pitus primaeva, With.), must certainly be placed in the 

 present group ; the broad transversely segmented pith is surrounded by 

 primary bundle-strands, which,* as in Araucaroxylon, are separated by 

 many medullary rays. The cortex, where its structure is preserved, is 

 marked by few special features ; its uniform parenchyma encloses a rather 

 large number of fibre-strands, and also shows here and there isolated 

 lumina filled with a dark substance, receptacles of resin or gum, as Renault 2 

 considers. Beautiful figures illustrating the anatomy of Cordaites will be 

 found in this author 3 . 



Peculiar casts of stems, to which Sternberg gave the name of Artisiae 4 , 

 have long been known to occur not unfrequently on the refuse-heaps of 

 coal-mines. These are cylindrical in shape but are usually flattened by 

 pressure, and are divided by deep transverse annular furrows into numerous 

 thin lamelliform segments which lie one on another like pieces of money in 

 a roll. They separate very readily from one another at the partitions. 

 Williamson 5 was the first to perceive that these casts fill the medullary 

 cavities of stems and branches with the structure of Araucaroxylon. There 

 is no longer any doubt on this point, since Grand' Eury 6 has shown that 

 they occur inside undoubted branches of Cordaites, and Williamson 7 and 

 Renault 8 have pointed out in the petrified axile portions the particular 

 structure of the pith on which their form is based. The constrictions there- 

 fore in these casts answer to the persistent margins of the diaphragms of 

 pith, which were broken through in the process of decay or were otherwise 

 partially destroyed before infiltration. The surface of the stems is usually 

 smooth, but angular forms and forms marked with transverse circles also 

 occur, like those for example figured by Grand' Eury 9 . It is a question 

 whether we may not be dealing in these cases with casts of the medullary 



1 Renault (1), t. 16, f. i. 2 Renault (1). 3 Renault (1), t. 15. 4 Sternberg, Graf von (1), Heft 1-5, t. 

 53. 5 Williamson (4). 6 Grand' Eury (1). T Williamson (l),ix. " Renault (1). 9 Grand' Eury (l),t. 28. 



