Manchester' McDioirs, Vol. Hi. (1908), No. 4. 5 



umbilicus represents the primary wood, the ratios of the 

 diameter of the wood to that of the branch would be 

 I to 8. 



Measurements of 9 petrified stems of similar dimen- 

 sions belonging to Lepidodcudroii fiiliginosuiii, L. sclagi- 

 noidcs Car. \iuxsciilarc Binney], L. Harcoiirtii and L. 

 Wuiischianniii gave I to 77 as the average ratio of the 

 diameters of wood and stem. I think that these ratios 

 are so close as to lend support to the view I have here 

 adopted. 



If the appendicular organ was only attached to the 

 umbilicus then it is very difficult to satisfactorily explain 

 the hole. 



It could I think be only explained by supposing that 

 the cortex of the appendicular organs penetrated into the 

 cortex of the stem ; it is not easy to see how this could 

 happen to the peduncle of a sessile cone. 



The branch theory has the advantage of explaining 

 easily the markings observed on the ordinary Ulodendroid 

 scars. 



These markings consist of a central or sub-central 

 point usually represented by a prominence on the 

 specimen. 



This umbilicus is surrounded by imprints or projec- 

 tions covering the surface of the scar ; these projections 

 are arranged so as to form a series of helices starting 

 from the umbilicus and passing outward to the edge of 

 the scar, forming, as Hugh Miller said, an engine- turning 

 pattern. 



They are, in fact, on at least the lower portion of the 

 scar, arranged exactly as the leaf traces are in a transverse 

 section of a Lepidodendroid stem. 



They have already been figured by Carruthers, 

 Kidston. and many other palaeobotanists. In circular 



