Monocot vs. Dicot Root Anatomy

Besides the predominance of tap roots in dicots and fibrous roots in dicots, there is a critical difference in the
vascular structure which relates to the derivation of the two root types ( tap vs adventitious).
Distinguish for yourself by observing the images below: the dicot with a stele similar to the protostele in the early
land plants, features a core of xylem surrounded by phloem, some parenchyma and then an pericycle/endodermis.
What is the function of an endodermis?

Dicot root anatomy:

Carefully observe how the branch roots originate from the pericycle in the image below: