They are called root primordia or adventitious roots and those folks who plant their plants horizontally do so b/c those rootlets form new roots wherever they touch the soil, which builds up a more extensive root structure which is good for water and nutrient uptake.

And yes, when cuttings are taken from a plant( and sucker cuttings are best) those wee rootlets form. I suggest not rooting cuttings in water, but using a solid matrix such as soiless mix etc,m b/c if you start in water the rooted cuttings just have to adapt to a solid matrix when you plant them anyway. Just my opinion.

Carolyn

Thank you Carolyn. You are the best.