I'm so sorry that it took me some time to respond. I was out of town this weekend. A customer commented on the lack of X and Z, several months back and my response to her is copied below. I am starting to go back and update some of my older products, and as I do I will make this more clear in the directions. In my newer letter matches (penguins and bunnies), I duplicated a couple of letters instead of eliminating letters. Thanks for your question.
"There was some thought put into this when the activity was designed, and I would love to explain why there is not a Y or Z on the trees. Four game boards were created. Because it would cause some drama with a group of children if some game boards had more letters/owls than others, it was very important that each game board have an equal number of letters. There are 26 letters in the alphabet, so this did cause a problem. I thought about putting duplicate letters on some game boards, but I felt that this would also cause some problems when a group of young children played. Who would get the first one that was drawn? For that reason, only 24 letters were used on the trees. I, however, included an x and z card so that children could identify and/or practice making the sounds of these letters when they were drawn. In the complete owl set that I sell in my TpT store, both capital and lowercase x and z cards are included with this particular activity so that children can also play match games with them."
April 14, 2013