Double Tipped Leaves

Leaves grow by producing cells from two special germinative parts called the apical meristem and the lateral meristem. The apical meristem is at the tip of the leaf. Usually, each leaf has a single tip, but I have come across a few leaves with double tips. This is like finding a four-leaf clover. It is hard to tell whether there are two collateral meristems or an apically driven leaf tip and a lateral growth that happens to parallel the dominant tip. Here are some examples. What do you think is happening in these departures from the standard, single tipped leaf?

I don't think the four leaves above are particularly good looking. I have found only a few double tipped leaves that have aesthetic appeal.

This is a small White Oak leaf. It's symmetry and leaf lobe elaboration are particularly eye-catching.

Below are two more small White Oak leaves. The leaf on the left appears to split into two growing tips. The one on the right seems to exhibit a side lobe (on the left side) which closely parallels the main portion of the leaf blade.

My favorite double tipped leaf is a Pin Oak, which has a lovely, nearly symmetric shape.

Below are two Tulip Poplar leaves. The one on the right is a standard shape. The one on the left appears to be a double tipped leaf, but it is so undeveloped that it might be a deformity. It also might not be a Poplar left. I found them close to one another, but the doubled leaf bears so little of the usual identifying characteristics that it's hard to tell. Call it a leaf oddity.