Friday puzzle uprooted!

Wow, we had some very creative answers on this one – and all of them made sense!  Peter, however, was spot on with his identification of roots (of a Thanksgiving cactus) growing in water (in an antique graduated cylinder).  I made it tricker by turning the photo upside down on Friday.  Here it is right side up:

What I love about this photo is that the various parts of actively growing roots are clear (more or less):  starting from the bottom you can begin to see the root tip and the hairless zone of elongation, followed by the zone of maturation with fuzzy root hairs, followed at the top by the area where lateral roots develop.</d