Apparently the word still has not made it into the dictionary!
OK, it's time that you all got an education on that subject. There are two kinds of seedlings. One is monocotyledon and the other is dicotyledon. Both words will be found in your standard dictionary. Cotyledons are the first leaves to emerge from the seed. Usually, they are very much unlike the second set of leaves which are called true leaves. Deviation from the normal is not common and in many cases is fatal. For example, a 3-lobed walnut or hickory nut is not uncommon but those seeds can never grow. It's Nature's way of not allowing her mistakes to continue.
Now we come to the tomatoes. With normal indeterminate varieties, perhaps there will be a tricotyledon at the rate of 1 in 4,000. Or you may grow thousands of seedlings per year and never see one in your lifetime. However, determinate varieties, such as most of the paste types, have different genes. One, although not named, is an acceleration gene which causes the plant to grow rapidly and produce a large number of fruit at one time. I have proven that it can be manifested right from the start with the seed producing 50% more growth immediately by producing an extra cotyledon. Being true cotyledons rather than two normal and one double, from a twin embryo, the tricotyledons also then produce three true leaves instead of the normal two. Throughout the growing period, growth will continue to be 50% more than normal.
We've already established that it is a fixed recessive gene in my variety. With time, I am certain that it would become a dominant gene and to the point where a normal dicotyledon seeding would be culled as being inferior. There has been only one tricotyledon study made and that was 80 years ago and with an indeterminate variety. It's never been researched with a determinate type until now. Four generations of mine has produced tricotyledons. Seed only saved from those plants. I fully expect 1 in 12 seeds to produce a seedling with an extra cotyledon. However, all of the seed that has been sent out this year is unproven as to the percentage of tricotyledons. It would disappoint me if everyone didn't end up with at least one or two per packet.
Accelerated growth? One test plant went into the garden on 3 June with just the three tiny cotyledons showing. 14 weeks later, the plant was worn out and dead after having produced 142 fruit. That is what is possible with the Paquebot Roma if given decent growing conditions.
Then, just when I have my hands full with the Paquebot Romas, there was a tricotyledon Riesentraube cherry tomato which showed up last year and gives me one more to play with!
Oh yes, you will not find tricotyledon in the dictionary. Not yet!