Manchester Meinoiis, Vo/. I. (1906), No. 10. 11 



vorkommen." Petioles so large as those of T. Sutclijfii 

 would be likely to remain unbranched for some distance, 

 and there is sufficient indication that in those further re- 

 moved from the axis branching took place, to conclude 

 that ultimately they may have ramified freely. 



5. The Petioles. 



The separation of the petioles from the main axis has 

 just been described, as have the slight changes in shape 

 undergone by the meristele during its passage out from 

 the main stele. The individual petioles are approximately 

 circular or oval in outline, with apparently no expanded 

 portion or side wing at the base of attachment ; their 

 rather irregular outline at times appears to be the result 

 of fossilisation. In some cases both stele and cortex are 

 wanting, and there is only a large clear calcite mass about 

 the shape and size of the petiole to represent it. 



The meristele of a medium-sized normal petiole in 

 most cases shews only the xylem in a good condition ; 

 between it and the preserved cortex is generally a gap 

 larger on one side than the other, which probably repre- 

 sents the phloem, but is also partly due to the tearing 

 away of the stele from the cortex, which is so common in 

 ferns. In transverse sections \hQ. protoxyleni groups stand 

 out conspicuously, and are chiefly on the outer edge of 

 the wood and on its convex side (see Fig. 8). In longi- 

 tudinal sections, although many tracheides are of the 

 simple scalariformtype,others arepitted like those described 

 for the main axis (see p. 5). In longitudinal sections a 

 few cells are suggestive of spiral protoxylems, though it 

 is doubtful whether they are so in reality ; there are 

 also a few cells which look like sieve tubes, but no trace 

 of actual sieve plates is to be found. Several sections 

 shew a zone composed of 3 or 4 rows of small thin-walled 



