venation

The venation is peculiar, and the disposition of the sori depends mainly on the peculiarities of the venation.

The fibro-vascular system in the leaf constitutes the venation.

The venation of the wings of insects is another example of modifications without serving any special purpose.

The compound leaves correspond to these modes of venation; they are either pinnately or palmately compound.

The thorax bears the two rather broad, membranous wings (Fig. 42) which have characteristic venation.