Manchester Memoirs, Vol. li. (1907), No. 8. 



15 



sible here to say definitely that it consisted of aerenchyma. 

 But the general concurrence with the transverse sections 

 leads me to suppose that this was the case, and I believe 

 we may conclude that the inferior scars were really 

 respiratory cavities, and were intended to reduce rather 

 than to accelerate the transpiration from the leaf-bases. 



Reconstructing from the series of tangential sections, 

 the appearance of the leaf-base as it would appear in a 

 radial section, one would get the appearance seen in Text- 

 fig. 7. This section is not quite median so as to show 

 the parichnos strand and the lateral pits. Projecting this 

 section on to a plan, one sees that it gives one the picture 

 of a typical leaf-base of a Lepidodendron. 



Fig- 7- — Reconstruction of the leaf cushion of a Lepidodendron 

 (probably Lep. Hickii) from four tangential sections similar to those 

 in Fig. 3 of Plate. 



v.b. = vascular bundle. lig.p. = ligular pit. par. = parichnos 

 strands. l.p.= lateral pits running into the leaf cushion below the 

 parichnos strands, ae. =aerenchymatous tissue clothing the top of the 

 lateral (respiratory) pits. In the radial longitudinal section on the left 

 hand side the membrane separating the two lateral pits is indicated by 

 oblique shading. 



