100 LYCOPODIALES [CH, 



Lower Carboniferous strata, it is seen to be continuous, as a 

 ridge with sloping sides, with a lower cushion (fig. 18o). 



Below a leaf-scar the cushion frequently shows a pair of oval 

 areas on which a fine pitting may be detected in well-preserved 

 impressions, these oval scars, as seen in fig. 185, D, are practically 

 continuous at the upper end with the parichnos scars on the 

 leaf-scar area; this is explained by the fact that these infra-foliar 

 scars also owe their existence to patches of lacunar, aerenchy- 

 matous tissue in close connexion with the parichnos K 



Shortly before entering the base of the leaf-lamina the 

 parichnos divides into two arms which diverge in the outer 

 cortical region right and left of the vascular bundle, and passing 

 obliquely upwards they come close to the surface of the leaf- 

 cushion just below the leaf-scar. The diagram — fig. 144, B — 

 shows a leaf-trace,tt,in the leaf-cushion, as seen in a diagrammatic 

 drawing of a vertical radial section of a stem, the dotted lines, 

 p, p', show the two parichnos arms which are represented as 

 impinging on the surface of the leaf-cushion at p', and then 

 bending upwards to pass into the leaf-base right and left of the 

 vascular bundle or leaf-trace. For convenience the arms of the 

 parichnos are represented in one plane though actually in 

 different vertical planes. 



Fig. 144, A, shows the difference between a view of the 

 original surface of a Lepidodendron, as at a, where a leaf-cushion 

 with a leaf-scar is seen, and a view of an impression representing 

 the outer cortex, b, a short distance below the surface. The 

 surface b, in fig. 144, A, corresponds to the face d — e in the dia- 

 grammatic longitudinal section fig. 144, B: the outline of each 

 cushion is clearly visible and in the centre is seen the leaf-trace, 

 It, with its parichnos. 



The surface-features, a (fig. 144, A), have been impressed on 

 the rock, c, (fig. 144, B) in which the specimen was entombed 

 and by the removal of the cast of the stem, that is the thickness b 

 to e in fig. 144, B, the form of the leaf-cushion is revealed. The 

 presence of the two infra- foliar parichnos scars at p' (fig. 144, A) 

 is explained by the diagram, fig. 144, B,p'. 



The relation of the parichnos to the oval scars below a 

 1 Weiss, P. E. (07). 



