Identification: Unknown brown branch plant, ID needed! tiny green leaves with white edges

Hi,

I need to know the ID of this plant. It's not doing too well, and I need to look up his/her specific care needs. He/she has think branches like a tree, with tiny green leaves with white edges. It is bipennate - one leaf always grows in oppostion of another, identical leaf.

I bought it from Rosemont metro plant/grocery shop a in early September in Montreal.

Any help appreciated! Thanks.

Andrew