from The Century Dictionary and Cyclopedia
- Of or relating to the perianth; provided with a perianth. Also periantheous.
Sorry, no etymologies found.
Schlechtendal  mentions a flower of _Fritillaria imperialis_ in which the perianthial leaves were relatively very small, and destitute of the usual nectary, while the stamens, on the other hand, were of their natural size and appearance.
From an examination of the structure of viviparous grasses Von Mohl was led to the conclusion that the lower palea is to be considered as a bract, and not a perianthial leaf, because the base of the palea surrounds the stem or axis of the spikelet entirely, and both its margins cohere towards its lower extremity. [