Manchester Memoirs, Vol. Ivii. (191 3), No. 18- 5 



In most parts of the section the walls appear entirely 

 without marking, but in some regions the cell walls are 

 impregnated with reddish brown colouring matter, and 

 then the walls are marked with distinct oval pits. There 

 is no indication in the longitudinal sections of the existence 

 of any transverse diaphragms such as are shown on the 

 specimens of Tylodendron from Prince Edward's Island, 

 described recently by Miss Holden.' 



The lignified tissues are found in the depressed regions 

 forming the boundary of the lozenge-shaped areas. In 

 places where the rhomboidal marking is indistinct on the 

 outside, this is due to a larger amount of the wood 

 having been preserved, so that the projecting masses of 

 the pith corresponding to the foliar gaps are not so clearly 

 shown. The short depression running up about a third 

 of the length of some of the areolae, and which has been 

 identified by Potonie as the leaf-trace, is also composed of 

 vascular tissue, and there is no doubt that Potonie has 

 correctly interpreted this feature of the Tylodendron cast. 



Unfortunately, the state of preservation of our speci- 

 men is not sufficiently good to make out all the details of 

 structure of the wood, but some features of interest can 

 be definitely ascertained. It will be seen, as shown in Fl 

 JI., Fig. 6, that small groups of tracheids arc found on the 

 inside of the main mass of secondary xylem, and 

 usually separated from it by one or more rows of 

 parenchyma cells. These groups are of small size. That 

 represented in P/, //., Fig^. 6, is one of the largest and the 

 best preserved, but they sometimes seem reduced to a single 

 tracheid. They are often surrounded by parenchyma 

 cells, which are drawn out radially from the group so as 

 to present a stellate appearance, not unlike the ground 



'^ Holder), Ruth. "Some Fossil Plants from E.istern Canada." 

 Annals of Botany, vol. .\xvii., 1913. 



