168 



LYCOPODIALES 



[CH. 



of delicate parenchymatous cells (m, figs. B and E, 181; C, figs. 

 183, 184) forming the meristematic zone^ The longitudinal 

 section represented in fig. 184 shows some recently formed narrow 

 tracheae, T, and beyond these the meristematic zone composed of 

 thin- walled short cells, C, arranged in horizontal rows. It is this 

 small-celled tissue to which the name phloem has been applied 

 by some authors^ a term which seems to me to be misleading 



Fig. 183. Lepidodendron Wiiiischianum. From the specimen shown in fig. 181 

 S, secretory zone; C, meristera ; T, immature tracheae. 



and inappropriate. In passing through this zone of dividing cells 

 the leaf-traces become surrounded by an arc of meristem from 

 which elements are added to the radially placed rows of secondary 

 tracheae. Beyond the meristematic region portions of the 



^ The term meristematic zone is used because some of the cells in this 

 region are in a state of active division, though the inner portion may consist 

 of permanent tissue. 



- Scott (00) p. 131 ; (08) p. 142. 



