Date: 26.01.2010

Hybrid Seedling:
A hybrid seedling is usually produced via the seeds using the hybridization process. Two different parents are used to produce the seeds. The seeds have their own character, usually a mixture from the parent plants. You need to wait till flowering to see the results. They are genetically different to each other and probably like the brothers and sisters in a family.

Meristem Seedling:
They are otherwise known as 'mericlones'. These are produced by cloning. As you can assume they have the same genetic make up of the parent plant and look exactly the same. They are like identical twins in a family.

In the current market mericlones tends to be costlier to produce than hybrids. This could change in a few years time.

Photos: Oncidium Meristem Seedlings or 'Mericlone'. As the name suggests they are clones or the 'identical twins' of the same plant

Patenting laws: Did you know that in the US the scientific names for the mericlones could be patented. However this doesn't apply to seeds. Hence, practically they could appear with different names in the market.
Ref: Q&A The Bulletin of AOS Jan 2010 Page 11