OF LOWER GBEENSAND PLANTS. 317 



credit for the careful and accurate series of sections he obtained. 

 These series of sections and a carefully rubbed-down piece of 

 the block itself proved beyond a doubt that the first radial 

 sections truly represented the astonishing fact, that the wood of 

 this plant consists of alternating series of secondary wood-zones 

 running alternately vertically and horizontally, so that in both 

 longitudinal and transverse sections zones of perfectly trans- 

 versely cut secondary wood are seen. 



This is shown in text-fig. 101 in a diagrammatic way, and is 

 illustrated in the text-figures and plates. 



The wood cylinder consists of: (a) the perimedullary zone, 

 in which short radial series and groups of tracheids are loosely 

 dispersed and ramify among large ground-tissue and medullary 

 ray-cells ; (b) the first ring of bundles of vertically running 

 secondary wood, forming a series of bays of wood much as in 

 Jlennettites ; (c) a series of cylinders of secondary wood alter- 

 nating, first a series in horizontal direction, then a series in 

 vertical direction, and so on, up to the number of nine or ten ; 

 and as the sections stop at the wood, snowing neither phloem 

 nor cortex, there is nothing to indicate how many more of these 

 cylinders there may be. The broad medullary rays, like those 

 in the Cycadophyta generally, run from one cylinder to the next, 

 apparently bending over at right angles with the wood. While 

 I am not quite certain of this, it appears that these alternating 

 series were the product of a single cambium, which for some 

 reason unknown, turned at right angles periodically. The 

 large simple leaf-bases running out through the zones of wood 

 tend to break into the regularly alternating series and carry the 

 transverse bands out with them a little, as can be seen in text- 

 fig. 107. But that the transversely running wood-zones in no 

 way depend on the leaf-traces, or are to be correlated with the 

 leaf-trace " girdles " in Cycads, can be seen in text-fig. 109, B, 

 where the leaf-trace l.t. runs right through the horizontally 

 running cylinder x. without disturbing it. 



The full consideration which these extraordinary structures 

 demand cannot be given here. The following short description 

 covers only the more essential facts of the anatomical structure 

 of the new species. 



The pith measures not less than 7'5 cm. in diameter, and pro- 

 bably more. It is apparently quite uniform in structure, com- 



