Why it's called 'Clock ' vine, I do not know. It doesn't resemble a clock, a watch or any other mechanical means of telling time. But I believe this species has the most dramatic floral presentation in the genus 'Thunbergia'.
I first saw this vine on a visit to a zoo-cum-garden establishment a few hours away from the city of Manila a few years back. It was vigorously climbing up a gazebo. The intertwining stems were so thick that it almost looked like the whole vine is the roof of the structure. The clusters of flowers, along with aerial roots (of another vine?) hang down inside the gazebo. Very neat!
The flowers are dangling under the roof of a gazebo. I hope to achieve this effect with our Clock vine someday.
Months after that we have our own Thunbergia mysorensis in our garden. It may not be as thick and robust as the one I saw but someday it will be. It's been trained to climb over a makeshift trellis and it's been growing well so much so that it started to bloom.