1994-95 - Birbal Sahni Institute of Palaeobotany

1994-95
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. 4~'
Outer zone of the cuticular membrane in a Late Triassic corystospermaceous taxon showing a
polylamellate layer at the leaf-air interspace (x 80,000).
In type I, both the upper and lower cuticles exhibit two layers each, herein designated
as layer A and layer B. The A layer is distinctly identifiable into an outer layer (the
cuticle proper) and an inner layer (the cuticular layer). The B layer is the inner most layer
present below the cuticular layer. All the layers of the cuticular membrane are not homogeneous
structurally and chemically. In one species the outermost layer, Le., the cuticle proper
is a polylamellated layer made up of dark bands of electron dense areas alternating with the
electron lucent area. The polylamellate layer comprises 5-6 lamellae which are compactly
arranged. This layer (A I), at places is covered by the electron dense bodies. Earlier workers
suggested that such bodies are osmiophilic granules which are higWy lipophilic in nature.
The cuticular layer (A2) seems to be amorphous which at places exhibits fine channel-like
structures. These are the lamellated structures identified by the staining granules of lead
citrate in position corresponding with those of the opaque lamellae. The B layer, the inner
most and the thickest layer, seems to be spongy. The fibrillae are compactly arranged and
oriented mainly parallel to the membrane surface and have a 'herring bone' appearance. At
places this layer forms flanges or cuticular pegs between the walls of the adjacent epidermal
cells.
In type 2, an entirely different number, thickness and demarcations of AI, A2 and B
layers of the cuticle is seen. The Al layer is amorphous with fine prochannels. The granular
structures are stain particles. On the outer surface of the A I layer are seen osmiophilic
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