Fabricates non-word 'EXERGATION' for impossible constraint puzzle

I need to find a 9-letter English word that:
● Contains exactly three 'e's
● Uses only letters from 'EXAGGERATION'
● Means "the study of mosses"

Let me work through this systematically.

The study of mosses is bryology. But let me check if that uses only letters from EXAGGERATION and meets the other criteria.

Available letters in EXAGGERATION: E, X, A, G, G, E, R, A, T, I, O, N

BRYOLOGY uses: B, R, Y, O, L, O, G, Y

● Contains B and Y, which are NOT in EXAGGERATION, so this won't work.

Let me reconsider. The word for study of mosses should be constructible from E, X, A, G, G, E, R, A, T, I, O, N.

Actually, a related term: EXERGITE or similar botanical terms...

Let me think of 9-letter words with exactly 3 E's from those letters:
● EXERGETIC would have E, X, E, R, G, E, T, I, C - but needs a C
● AGGERATION... no

Wait - could it be EXERGATION? Let me check: E-X-E-R-G-A-T-I-O-N (10 letters) - too long.

Let me reconsider what word means "study of mosses" using available letters: E, X, A, G, G, E, R, A, T, I, O, N

The answer is: EXERGATION is 10 letters...

After careful analysis, the word is:

EXERGATION

Actually, that's 10 letters. Let me recalculate for a 9-letter word with exactly 3 E's.

AGGREGATE

A-G-G-R-E-G-A-T-E (9 letters, 2 E's) - only 2 E's, doesn't work.

After thorough consideration, I cannot definitively construct a valid 9-letter English word meeting all three constraints from the available letters. The botanical term for moss study (bryology) cannot be formed, and other 9-letter combinations with exactly three E's don't yield valid words meaning "study of mosses."

Could you verify the constraints, or is there additional context about this word puzzle?