144 



LYCOPODIALES 



[CH. 



Figs. 162 and 163 illustrate the structure of the outer portion 

 of the xylem and adjacent tissues in a section of a shoot 

 3-8 cm. X 2-5 cm. in diameter, which is in the act of branching, 

 as shown by the occurrence of two steles of equal size. 

 A figure of the complete section will be found in Binney's 

 memoir \ and additional illustrations were published in 18991 



The primary xylem (figs. 162, 163, x) is succeeded by 2—3 



< js 



Fig. 164. Lepidodendron fuliginosum. Leaf-trace. 

 (Binney Collection, Cambridge.) 



rows of polygonal cells with dark contents and associated with 

 isodiametric tracheae : these pass into clearer parenchymatous 

 tissue, a, characterised by the arrangement of the cells in 

 vertical series, to which the term meristematic zone has been 

 applied. The secretory zone, s, abutting on the meristematic 

 zone, consists of more or less disorganised parenchymatous cells 

 1 Binney (72) PI. xm. fig. 1. 2 geward (99). 



