DESCRIPTIVE CATALOGUE 



possible to trace a single radial series of tracheids through an 

 angle of 90, running iii the same section, first as a transverse 

 and then as a vertical series. One and the same medullary ray 

 also can sometimes be followed, first in transverse and then in 

 radial longitudinal section, which later again turns to true 

 transverse. The inference is therefore drawn that there was 

 but a single cambium, which had periodic changes of direction. 



In tangential section the tracheids are geen to follow a very 

 contorted course, sometimes to double back on themselves, 

 and even to branch and loop in various ways (PI. XXX L, 

 rig. U). This takes place not only in the neighbourhood of the 

 leaf-traces, but apparently all through the wood, and more 

 especially in the regions where the tangentially and horizontally 

 running cylinders merge. 



Medullary rai/st are very numerous. They are principally 

 Iriseriate, a few are invgularly multiseriate by the addition of 

 two or three extra cells. They are various in height, many 

 being as low as 4, or as high as 30 cells in vertical series, the 

 majority averaging about 20 cells high. The individual ray 

 cells arc large, up to about GOxl5U^or more; with nearly 

 straight end -walls, and apparently without special thickening or 

 pitting of any of the walls. I have seen something suggestive 

 of large oval pits in several of the radial walls, but cannot feel 

 sure that they arc not pet ri fact. 



Many of the larger ray-cells show the most beautifully pro- 

 served vacuolated protoplasmic contents and nuclei which I 

 have ever seen petrified. They rival the most carefully fixed 

 living material. 



/'/them and cortical tissues are not preserved. 



The leaf-traces are conspicuous in every section, and arc largo 

 and numerous (text-figs. 109, 110, and 111). The individual 

 trace is a solid oval-cylindrical mass as it passes nearly straight 

 out through successive zones of wood (text-fig. 10913, ?/.), and 

 curves very slightly upwards in its course. In actual distance 

 the leaf-traces are about 1 cm. apart, apparently arranged in 

 regular spirals (text-fig. 110). The traces vary somewhat 

 in size, but average about 3 mm. across by 4-6 mm. in vertical 

 height. Each trace consists of a compact mass of tissues much 

 resembling the ground-tissues of the perimedullary zone, but 

 more compact and smaller-celled. The gum-canals of the pith 



