We're having a problem with our purple clematis. It appears to be perishing from the roots up. The leaves at the base of the plant started turning brown approx. 10 days ago. In the last two days the condition has accelerated to where 3/4 of the plant is turning brown, and the whole plant seems to be under stress. Help!

It sounds like your clematis has the dreaded disease known as 'clematis wilt'. It enters through a break in the stem, and moves through the plant quickly. There is not much that can be done short of cutting it below where the infection has started, and waiting for the plant to regenerate from the roots. It will quite often do this.