[MargaretR]

http://www.organicgardening.com/feat...6-1576,00.html
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Built-in bitterness. Most cucumber plants contain compounds known as cucurbitacins ("kyew-ker-BIT-a-sins") that cause fruit to taste bitter. At low levels, you aren't likely to detect them. But high levels of cucurbitacins produce extremely bitter fruit- so bitter that eating it would cause a riot in your stomach. Cucurbitacin levels increase when a plant is under stress. The concentration of these compounds varies from plant to plant, fruit to fruit, and even within the individual fruit itself. The ability to taste cucurbitacins also varies from person to person. Even insects have varying preferences for cucurbitacins- the compounds attract cucumber beetles but repel other insects, such as aphids and spider mites.

http://www.telegraph.co.uk/news/news...uce-burps.html

http://www.hort.purdue.edu/ext/bittercukes.html
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Most cucumber plants contain a bitter compound called cucurbitacin, which can be present in the fruit as well as the foliage. Bitterness in cucumbers tends to be more prominent when plants are under stress from low moisture, high temperatures or poor nutrition.
For some cucumber eaters, the bitter taste can be accompanied by a digestive discomfort known as a burp. Some of the newer cultivars of cucumbers do not have the bitter compound and, thus, no burp. So, some seed companies called their bitter-free cukes "burpless."

PS I have nothing better to do today