JET. 71 



51,593, 51,594. Pure jet similar to ttat shown in PI. VIII. 

 Pig. 3, but in this case the arrangement of the longer dark bands 

 across the fainter vertical lines shows that the section has been cut 

 in a radial longitudinal direction. 



51.596. Eadial longitudinal section of jet, but darker and less 

 transparent than 51,593 and 51,594. 



51.597. Probably a tangential longitudinal section, similar to 

 that shown in Fig. 3, PI. VIII. 



51.598. Longitudinal radial section showing the tracheal walls 

 as vertical lines crossed at right angles by rows of dark dots 

 representing medullary-ray cells. 



Fig. 7. — Coniferous wood partly converted into jet. Highly magnified. 51,448. 



51.599. Transverse section like that reproduced in Text-fig. 7, 

 but darker. 



51.600. A good example of pure jet in transverse section ; the 

 rich sherry - coloured matrix is traversed by parallel contorted 

 bands, as in PI. VIII. Fig. 7, and shows traces of the tracheal 

 walls as a faint network of fine lines. 



51,621. A small section of jet almost entirely without signs 

 of structure. Under a high power it presents the appearance of 



