The topmost layer of the crown of tall trees is called .

Solve the crossword puzzle with the help of clues given:

ACROSS
1. Dead and decaying dark-coloured organic matter (5).
2. The sequence of who eats whom (9).
3. The branchy part of a tree above the stem (5).
4. White coloured fluffy fibre (6). 

DOWN
5. Light yellow coloured excretion from certain trees (5).
6. Shorter trees forming different layers under the Canopy (11).
7. Plant having a life span of two years (9).
8. The organisms which make their own food from CO₂ and H₂O in the presence of light and chlorophyll (9).