MEDULLOSEAE 443 



other tissues, that the original polystelic organisation 

 sinks, as it were, into the background. 



In some exceptional instances, additional complica- 

 tions made their appearance. This was the case, for 

 example, in a huge specimen of Medullosa stellata (var. 

 giganted), the largest as yet discovered, the stem of which, 

 though decorticated, was over a foot and a half thick. 

 The central ground-tissue, 5 or 6 inches in diameter, was 

 traversed by forty-three central steles, some of which 

 were an inch in diameter. The peripheral zone of 

 steles was enormously thickened on its outer surface, 

 but, in addition to this, there were three concentric 

 extrafascicular layers of wood and bast, which had 

 been formed successively around the whole of the 

 normal vascular system. Thus, in this specimen, the 

 anomaly characteristic of the recent Cycadean genera, 

 Cycas, Macrozamia, and Encephalartos , co-existed with 

 the polystelic structure of a Medullosa} 



It is evident that some of the Permian Medulloseae 

 reached the dimensions of fair -sized trees ; others 

 appear to have had long and comparatively slender 

 stems ; it has been conjectured that some of the latter 

 may have been climbers, like the lianes of tropical 

 forests, but for this supposition there is no real evi- 

 dence. The resemblance of the anatomical structure 

 of the Medulloseae to that of the stems of certain 

 climbing Sapindaceae, pointed out in 1 8 8 1 by Goppert 

 and Stenzel, 2 is more apparent than real. Some of the 

 Sapindaceous lianes have a number of vascular cylinders 

 in the mature stem, but this is merely an anomaly of 



1 See Weber and Sterzel, I.e. 



2 " Die Medulloseae, eine neue Gruppe der fossilen Cycadeen,'' Palm- 

 ontographica, 1881. 



