420 PSAKONIEAE [CH. 



resemblance to those of P. Sterzeli, which are as yet known 

 only in a sterile state. 



Psaronius hrasiliensis Unger, a species founded by Unger 

 on a piece of silicified stem acquired by Martius in "Brazil and 

 now in the Rio Museum, is a good example of a tetrastichous 

 species. Solms-Laubach^ has recently told the history of this 

 type, which is represented by sections, cut from the Rio stem, 

 in several European collections. A well-preserved section in 

 the British Museum is figured by Arber^ in his catalogue 

 of the Glossopteris flora and by other authors. Scott gives 

 a concise description of the species in his Studies in Fossil 

 Botany^. The roots of P. hrasiliensis are stated by Pelourde* 

 to have a lacunar cortex. 



Psaronius musaeformis Corda"*. Fig. 296, D. 



This species from the Lower Permian of Chemnitz and the 

 Coal- Measures of Bohemia affords an example of the distichous 

 tjrpe in which the leaves are borne in two rows. The vascular 

 bands, as seen in a section of the dictyosteles, occur in regular 

 parallel series. The stelar region is separated from the cylinder 

 of encasing roots by a sclerenchymatous sheath, broken at 

 intervals where roots pass out from the vascular region. 



Psaronius coalescens' (fig. 296, C) illustrates a somewhat 

 different arrangement of vascular tissue which approaches more 

 closely to the polycyclic structure characteristic of sucl> recent 

 ferns as Matonia and Saccoloma. A still closer resemblance to 

 the solenostelic type is seen in Psaronius Renaulti from the 

 Lower Coal-Measures of England which Scott' describes as 

 characterised by a single annular stele, interrupted only by 

 the exit of leaf-traces. As he points out, it is noteworthy that 

 this species is distinguished by the simplest form of stele met 

 with in the genus ; it is the oldest species and may be regarded 



1 Solms-Laubaoh (04). = Arber (05) PL vn. 



' Scott (08) fig. 113; Zeiller (90) p. 246, PI. xxi. fig. 1. 



^ Pelourde (OS^). = Stenzel (06) PI. vi. ; Goeppert (64) A. ; Stenzel (06). 



» Zeiller (90) PI. xiiii. ' Scott (08) p. 301. 



