Galleries are sort of like plant species: Some are perennial and blossom anew each season, others are annuals that blossom briefly before fading away. The Ellen Curlee Gallery, we now know, belonged to the latter class. But oh, what a bloom it was! Concentrating on modern fine-art photography, the tiny space on Washington Avenue downtown became known for mounting intellectually rigorous shows that often presented several artists — both homegrown and from outside the region — tackling a single issue or idea from radically different points of view. The effect was often heady, and the gallery garnered its share of critical acclaim. But acclaim doesn't pay the bills, and last May, after a three-year run, the gallery's eponymous owner called it quits. But it turns out Curlee herself is something of a perennial: This fall she'll open a new, less formal project space just down the street.