System Information
Operating system: Windows-7-6.1.7601-SP1 64 Bits
Graphics card: AMD Radeon HD 6290 Graphics ATI Technologies Inc. 4.5.13399 Core Profile Context 15.200.1062.1004

Blender Version
Broken: version: 2.81 (sub 13), branch: master, commit date: 2019-10-04 13:28, hash: rBd590db83705b
Worked: (non-applicable)

Short description of error
The hair particle system doesn't emit on array instances. However, if you put the Array modifier before the particle modifier, the hair only emits on the last instance of the array.

Exact steps for others to reproduce the error

• Add a hair Particle system to any object
• Add an Array modifier to the same object
• Place the Array modifier before the Particle modifier