2 WEISS, The Parichnos in the Lepidodendracece. 



central vascular bundle ; but this view was shown to be 

 erroneous by Renault ('75) > wri o found that in Sigillaria, 

 at all events, the tissue coming to the surface at these 

 points was parenchymatous and not vascular. 



As these lateral marks in Sigillaria agreed so closely 

 with those of Lepidodendron, it was clear that they were 

 homologous structures, and consequently here, too, as 

 Solms-Laubach ('91) pointed out, they could no longer 

 be considered as vascular. Subsequent investigations by 

 Bertrand ('91) and Hovelacque ('92) have shown that both 

 in Lepidodendron Harcourtii and in Lepidodendron sela- 

 ginoides these parichnos-scars communicate with strands 

 of parenchymatous cells in the leaf cushion as is the case 

 with the similar lateral scars in Sigillaria. If one traces 

 these parichnos strands through the leaf base into the 

 stem, one finds that they unite in the leaf base into a 

 single somewhat kidney-shaped strand which, running on 

 the underside of the vascular bundle, penetrates together 

 with it the periderm and the hard outer cortex, and joins 

 the soft and often lacunar middle cortex of the stem. 

 This can be seen from the series of excellent drawings 

 made by Hovelacque of the leaf trace of Lepidodendron 

 selaginoides at different positions in the cortex, whence 

 we can discern that the parichnos makes its appearance 

 as a parenchymatous strand, accompanying the leaf trace 

 on its entrance into the outer cortex fecorce moyenne ' of 

 Hovelacque). (See Hovelacque ('92) Text-figs. 35 to 37.) 

 Similar figures of the course and bifurcation of the 

 parichnos strand have been figured by Williamson in 

 the case of Lepidophloios fuliginosus. (See Williamson 

 ('93). Figs- 3i to 37). 



None of these figures, however, show the actual 

 union of the parichnos strand with the middle cortex, 

 though this continuity was recognised by the above 



