of Coal-Measure Plants. 



149 



tracheids, at s the dark secretory elements, and between the two 

 groups a clear space originally occupied by thin-walled paren- 

 chyma. 



Slide 3. Text-figure 4, PI. in. figs. 1 and 2; PL iv. figs. 7 

 and 10. 



This transverse section, which agrees in essential characters 

 with Sections 1 and 2, is figured by Binney in his PL XV. fig. 1 ; 

 it is slightly crushed ; the longer diameter measures 4'2 cm., and 

 the shorter diameter 34 cm., the longest diameter of the elliptical 

 stele being 1*2 cm. The pith has been to a large extent destroyed ; 

 the xylem exhibits the same characters as in the previous sections, 

 but many of the tracheids are full of a vacuolated substance 

 which may probably be regarded as the product of some patho- 

 logical change (Text-figure 4). 



Figure 4. 



Transverse Section, showing the Vacuolated Contents in the 

 Primary Tracheids. (Slide 4, x 100.) 



The middle lamella of the large primary tracheids is clearly 

 preserved as a dark line, as shown in Text-fig. 4, but the greater 

 part of the lignified wall has in many places suffered considerable 

 decay. At the edge of the corona, or slightly internal to the 

 xylem, a few isodiametric reticulately marked tracheids are met 

 with, as in the other sections. The meristematic and secretory 

 zones agree in structure with the corresponding tissues in the 

 other sections. The broad middle cortex is particularly well 

 preserved, and exhibits the trabecular structure of the paren- 

 chyma very clearly; there is no phelloderm, but the junction 

 of the middle and outer cortical regions is very clearly shown, 



