michael adams writes


I've got some really old opuntia microdasys with very long chains
of pads, all grown from seed. And as you know the spines are
in the glochids, the brown felty buttons. You can brush
against them without noticing, and only afterwards do you
notice the irritation on your skin.

By which time you've transferred them from the original site to every
intimate part of your body.


--
Kay