All of the cucumbers that I know of have both male and female flowers, though they may alternate in which they produce, to ensure cross pollination in nature. Some of the older burpless greenhouse cukes came with "male" and "female" seeds in separate envelopes in the packet, or with the "male" seeds dyed to distinguish them. They both produce both kinds of flowers, but the "females" are the ones that produce burpless, seedless fruit--but only when pollinated by the "male" variety's male flowers. The "male" variety's female flowers produce normal fruit with bitter seeds, and the "female" variety produces ordinary slicing cukes when pollinated with their sisters' male flowers.

Tugbrethil. Am I doing right then ,by nipping Male flowers off .Heard if left on causes Cucumbers to become bitter

Thankyou for your comments

Newer varieties of greenhouse cukes don't need pollination to produce fruit, so go ahead and pinch off the male flowers. the one that is producing only males is probably just going through a phase--they do that when they first start blooming, or if the temps are too high. The latter is common here, but rather rarer in the UK! :)

I always nip off the male Pammie, they can cause the cucumbers to taste bitter if left, can be time consuming but I really don't like bitter cucumbers.....

Yes very time consuming Lincslass flowers keep appearing so quick from no where .But Cucumbers are growing well ,eaten 4 or 5 upto now.

I've usually grown the naturally non-bitter cucumbers, such as Armenian--which is actually a cucumber-flavored melon--or 'Telegraph', or 'Tasty Green'. That's partly because of the taste, and partly because they are more heat tolerant.