This is a night-blooming plant,<i>Epiphyllum hookeri</i>. The bloom opened well after dark, and was droopy by the next morning. I also think it is interesting to note that all of the stems are green except this one section from where the flowers are blooming.
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/12376942@N08">Justin Leonard</a>
CC BY 2.0
<p><a rel="nofollow" class="external text" href="https://www.flickr.com/photos/scrap_pile/5122759229/">Unidentified plant #2</a>
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<ul><li>Uploaded by <a href="//commons.wikimedia.org/wiki/User:Uleli" title="User:Uleli">uleli</a></li></ul>