Difference between True and False Indusium

Indusium is a delicate membranous structure that protects the sporangium or sorus in pteridophytes
Based on the origin, Indusium may be true or false.
True indusium:

In the figure, solid red circle – True indusium

1. A delicate membranous structure arises from the lower side and covers the sorus of sporangia (refer figure)
2. Originates from the lower side of the pinnae as an epidermal outgrowth
3. Specialized structure formed on the lower side of pinnae for protection of sorus
4. Seen in Dryopteris
False indusium:

In the figure, solid red circle –false indusium originating from the margins

1. It is formed by the curving of margins of the pinnae or leaflet that protects the marginal sorus.
2. Originates from the upper side of the pinnae.
3. Formed by the curving of margins of pinnae.
4.  Seen in Pteris, Adiantum