The area of the cushion excluding the leaf-scar is spoken of by some writers as the field. Below the leaf-scar the kite-shaped cushion tapers to a gradually narrowing basal position: in _Lepidodendron Veltheimianum_, a species characteristic of Lower Carboniferous strata, it is seen to be continuous, as a ridge with sloping sides, with a lower cushion (fig. 185). 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, aerenchymatous tissue in close connexion with the parichnos[243]. 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, _lt_, 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 diagrammatic longitudinal section fig. 144, B: the outline of each cushion is clearly visible and in the centre is seen the leaf-trace, _lt_, 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′_.