The mass of cells within the integuments is called:

The correct answer is Option (4) → Nucellus

An ovule is attached to the placenta by a stalk, the funicle. It has one or two protective coverings called integuments. The integuments surround a central mass of cells called the nucellus, leaving only a small opening at the tip, the micropyle. The cells of the nucellus store plenty of reserve food, and the embryo sac (female gametophyte) lies inside the nucellus.

NCERT Extract:
The Pistil, Megasporangium (Ovule) and Embryo Sac – “… Each ovule has one or two protective envelopes called integuments. Integuments encircle the nucellus except at the tip where a small opening called the micropyle is organised. Opposite the micropylar end, is the chalaza, representing the basal part of the ovule. Enclosed within the integuments is a mass of cells called the nucellus. Cells of the nucellus have abundant reserve food materials. Located in the nucellus is the embryo sac or female gametophyte.”