rsAROxius. 149 



Co-types. The earliest specimen, figured by Unger (jS"o. 1446, 

 Museum d'histoire naturelle, Paris), is an imperfect fragment, 

 showing only the pseudo-cortex. Although, strictly speaking, it 

 is the type-specimen, it is impracticable to regard it as such, 

 since it does not include the central vascular cylinder. There is 

 also a suspicion that it was derived from the same stem in Brazil 

 as all the other specimens now in various European museums, 

 but it is not quite certain that this is the case. The real 

 type would appear to be a large stem in the Museum at 

 Bio de Janeiro, Brazil. From this trunk slabs have been cut at 

 various periods, among which are those in the Museum d'histoire 

 naturelle (No. 1445) described by Brongniart, who gave the first 

 adequate description of this species ; those in the British Museum 

 (V. 9002 and V. 5388), all of which, I believe, are now in the 

 Geological Department ; and those at Strassburg. Solms-Laubach 1 

 has recently traced in great detail the history of these specimens. 

 It would perhaps be best to regard the Bio specimen and its 

 derivatives in Paris, London, and elsewhere as co-types with 

 Unger's specimen. 



Central vascular cylinder surrounded by a continuous and closed 

 sclerenchymatous sheath. Peripheral steles four in number, 

 separated in part from the central region by sclerenchymatous 

 bands, slightly curved outwards, with inrolled extremities, or some- 

 times folded in the form of a ring. Steles of the central region, 

 lying internal to each of the peripheral steles, two or three in 

 number, strongly curved, arranged radially, often divided into two, 

 sometimes forming a closed ring. Steles lying between the 

 peripheral steles, and often anastomosing with them at their 

 extremities, more or less bent, longer than those nearer the centre 

 of the cylinder. 



Leaves disposed in four vertical series, probably in opposite or 

 sub-opposite pairs. Leaf-traces on leaving the cylinder having the 

 form of an open curve, with extremities bent in a hook -like manner. 



Conjunctive tissue of the central cylinder and pseudo-cortex 

 continuous. Inner cortex of roots not lacunal, apparently often 

 containing numerous gum-canals arranged more or less in a circle. 

 Vascular cylinder composed of 6-8 bundles. 



1 Solms-Lauback (04). 



