Which kind of tree produces the hardest wood?
The hardness of wood can be measured by the "Janka hardness test" developed by Gabriel Janka.
The highest value measured currently is the Australian "Allocasuarina luehmannii" (also called buloke or bull-oak).
Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:

Which kind of tree produces the hardest wood?

### Response:

The hardness of wood can be measured by the "Janka hardness test" developed by Gabriel Janka.
The highest value measured currently is the Australian "Allocasuarina luehmannii" (also called buloke or bull-oak).
