Select Color Range not functioning as expected

Here is an image to which I want to make some localized adjustments.  I thought I would use the Select Color Range tool to isolate the dark green trees along a ridge at the base of Mt. Ranier.  I'm eventually making this into a B&W unage and want to be able to control the density of some specific areas.

Here's an enlargement of the area I want to select from, only selecting the dark green trees.

In the end, when I applied the Select Color Range tool to the dark green trees I didn't get what I expected.  I started with Fuzziness set to 0 and Range set to 0 thinking this would provide the greates limitation on pixels selection.  I first used the left eye dropper to select an initial color, then I used the middle eyedropper to add more of the dark green trees to the selection.  What seemed odd was that the first selection with the middle eyedropper appeared as a square.  Each time I added a little more from an adjoining area the square had another rectangle added to it keeping it a square.  As I moved closer to the edge of the dark greek trees, instead of selecting only the dark green trees, it added another rectangular area to the side that included the trees and other parts of the image which were not dark green.  I had expected to get an irregular shape that was mostly the dark green trees and from there I could adjust the Fuzziness and Range values upward to get the most useful selection.  I didn't seem to work that way. 

Here's a closeup of the selected area.

Here is the mask that was added to a Brightness/Contrast layer as a result of this selection with the Fuzziness set to 0 and Range set to 0.

I've used this approach on other images and it seemed to work as expected on some and not on others.

What am I missing in this siuation?