The longest running plant sale at the garden occurs today and tomorrow: the 29th Annual Indoor Plant Sale. I had a grand time yesterday trying to photograph a few of the plants available, since I don't often get the opportunity to work with indoor plants.
A native of southwestern Africa, “string of beads” grows in arid habitats. The succulent beads are actually the leaves, modified for living through extended periods of drought. Dr. T. Ombrello of Union County College has written an intriguing article on the adaptations of this Senecio and the closely related Senecio herreianus, entitled Senecios, With Windows in Their Leaves. The narrow bands you can see on some of the beads consist of transparent tissue to allow light to penetrate the interior of the bead and increase photosynthesis without increasing water loss.
It might be worth revisiting my comments on diversity within the Asteraceae in the BPotD entry on Raoulia australis. There is simply an amazing amount of diversity of form and structure in this plant family.