4 Stopes, a Nezv Fern from the Coal Measures. 



(which is furthest from the growing region), most of which 

 must have been attached some distance further back 

 along the rhizome beyond the fragment now in our 

 hands. 



The internal anatomy is simple for so large a plant, 

 there being but a single solid stele in the main axis, and 

 a simple band of vascular tissue in the petiole, in neither 

 are there definite sclerised bands, though the outer cortex 

 is somewhat thickened. 



The preservation throughout is of that curious type 

 well known to palsobotanists as " roof preservation " (see 

 p. 17), which affords local patches of tissue exquisitely 

 fossilised with every detail retained, and other parts 

 entirely wanting. From this cause, the work of recon- 

 structing the plant has been extremely difficult, for in one 

 section the axis bundle or whatever is being studied may 

 be well preserved, while in the neighbouring sections of 

 the series no trace of it may be seen. This partly accounts 

 for the many instances in which it has been impossible to 

 speak quite definitely about a point under discussion. 

 Such difficulties are always encountered to a certain 

 extent in fossil work, but in " roof nodules " of this type 

 they are more serious than usual. 



3. The Main Axis. 



Although it is a little difficult to determine the exact 

 limit of the cortex, the diameter of the main axis appears 

 to be just short of one centimetre. Its external form is 

 approximately cylindrical, broken at frequent intervals 

 by the off-coming petioles. The external surface was 

 apparently smooth, but the petioles are so closely arranged 

 that but little of it would be exposed. 



The stele is a single nearly circular one, of the 

 simplest monostelic type. The xy/on mass is absolutely 



