Anno 2014 the number of natural hybrids in Cryptocoryne is estimated on about 25 % of the known natural populations found in nature. Some hybrids as for example C. x purpurea nothovar. purpurea are known for many years - and often have a wide distribution. Many hybrids are discovered in the last few decades and many of these are only known from one locality. A number imported plants who are suspected to be of hybrid origin are never found again in nature - maybe it has disappeared or that one locality is overlooked as for example C. decus-silvae or C. zukalii.
Many hybrid plant are sterile and for that will not develop fruits and can only propagate vegetative by runners. As for a Cryptocoryne the fruit is never found, the plant may be a hybrid. Especially suspect are plants with intermediate characters in its morphology. When the plant flowers, either collected in nature or grown in cultivation, one can take the pollen to check it on fertility. A low pollen fertility near zero percent indicates fully sterile plant. Many plants however are not fully sterile and so may propagate. It also happens that plants with a different chromosome number hybridise giving birth to a plant with an intermediate number. Finally a dna investigation may clear up what happened. Another approach is to 'synthesize' hybrids in artificial crossings. In the past 40 years, Jacobsen from Copenhagen university made some 1000 successful crossings.
Hybridisation may occur many times separately in nature. As the parents from different localities show variation, the offspring also does.
hybrid vigour
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