Do you mean cross pollination between other varieties? Or cross pollination between other species? The latter doesn't happen, as far as I'm aware.

OK. Say your friend/someone who gave you the seeds says that the seeds are "X" variety. The chances are very high that they are pure. BUT there is NO WAY to verify it, until you harvest tomatoes from the plant(s) grown from those seeds. Even then the effect of CROSS POLLINATION (if any) might not be so obvious, unless you are a tomato expert.

If asking about X pollination between tomatoes go to the top of this page, click on FAQ's and scroll down to find the best article I know about it that's called How To Prevent Cross Pollination.

You'd only detect X pollination from saved seeds of fruits that had been X pollinated in one season and those saved seeds planted the next season.

And you sure would know you had X pol since the plants you grew from X pol seeds would be very different from what you started out with from the original plant.

Of course that depends on what the X pol male parent was, as to traits, meaning if a red X pol a red, it might be hard to tell.

Carolyn

how could you tell?

If they were crossed before you bought the seeds? The simple answer is you couldn't tell. There are numerous variables to be examined and unless there is a really obvious change from the norm you'll never know - unless you want to get the DNA tested. :).

What is the name of the variety? That is the place to start. Then look up that name and learn what the characteristics of that variety is supposed to be - the shape of the leaves, the size of the fruit, the color of the fruit, the shape of the fruit, the shape and number of the locules inside the fruit, etc. etc. and those are just the obvious to the naked eye issues.

Dave