There really are many answers to this in the world of botany.
In this case I am referring to the puzzling plant, Epiphyllum oxypetalum.
This leggy plant sprawls as it grows. It is in a heavy pot for balance not for root room.
Mine has not bloomed yet, but I am enjoying its peculiar habit of growth.
When is a leaf NOT a leaf? When it’s a stem.
The orchid cactus has flattened stems that look like leaves with thick veins.
When new leaves pop out from the ends of these veins,
you realize that the leaf was a stem.
Epiphytes that live in trees have different rules than ground plants.
A stem has to serve as a leaf and a stem.
Another lesson in life from a plant.