Tree Sap Droppings

Riding my bicycle Saturday morning I noticed a number of times that I rolled over tree sap. The sound of the tires were completely different.

Here is an example of tree sap on the road on the left of the road and the right side of the road is dry.




And this is the culprit Black walnut.






Here is a Red bud tree growing under a Black walnut tree. The red bud tree is saturated with sap, but it seems to be from the Black walnut.