Perisperm is
a. Degenerate part of synergids
b. The peripheral part of the endosperm
c. Degenerate part of secondary nucellus
d. Remnant of nucellus

Hint: Some tissues of the parent plant body do not degenerate and are meant for providing nutrition to the developing seed.

Complete step-by-step solution:
Perisperm refers to the remnants of the nucellus left after the fertilization of seed.
1. The perisperm is a diploid parenchymatous tissue modified for the storage of foods.
2. The perisperm is functionally similar to the endosperm.
3. It is mainly composed of starch and a little amount of fat. It completely lacks protein.
4. It is characteristically found in the families Piperaceae, Caryophyllaceae, Zingiberaceae, and Nymphaeaceae. It is thus seen in black pepper, beet, nymphaea, Amarnath, etc.
5. It is also found in some gymnosperm families like Gneticae and Taxaceae.
6. It can either form a part of the reserved food material along with the endosperm or the complete reserve food material.
7. The presence of perisperm is an adaptive feature that helps the seed to procure its food until the seedlings develop and become able to photosynthesize.

So, the correct answer is Remnants of the nucellus.

Note:
a. Seeds having perisperm for nutrition are known as a perispermic seed.
b. They are found near the micropylar end of the seed.
c. The nucellus gives rise to megaspore mother cells which later undergoes reductional division from the female gametophyte.
d. In some cases of Apomixis, the cells of the nucellus may directly give rise to the embryo. This results in the formation of seeds without fertilization.