ants don't carry leaves, but only a part of it, in fact they have a mouth with tooth for this!
I have lived in Central america in the past and I have seen large ants that were totally capable of handling entire leaves.
Perhaps entire leaves, but you do very, very rarely see them with the stem. Perhaps every once in a blue moon, but not that often.
They definitely wouldn't hold them by the stem either.
Well in costa rica there are thousands of little shits swarming my yard and they get into my house too. Maybe I will take some photos next time I go back to see if any have stems. X'D