from the June 29, 2007 Newsletter issued from Sierra Gorda Biosphere Reserve, QUERÉTARO, MÉXICO
SPINES ON SPINES ON SPINES
andering on the scrubby slopes here you don't want to lose your balance and grab at the stem shown below:

Not only does the stem shown there possess spines on spines on spines, but also the final spines are curved so that anything that gets punctured will probably get ripped, too. This is one of the most aggressively spiny stems I've ever seen. But spininess isn't this plant's only distinction: It's also a perfect example of a "half tree, half vine" state.

If you follow the spiny stem in the picture upward you'll see that soon itz branches soon start leaning into neighboring trees, and eventually become so slender and lithe that they really are nothing more than vines. You can see a viny, leafy branch-tip at the right.

The plant is PISONIA ACULEATA, a member of the Four-o'clock Family, the Nyctaginaceae, along not only with Four-o'clocks but also Bougainvilleas. Of course in English it's known as Cat-claw and Devil's-claw, but the name that seems to appear most in the literature is "Pull-back-and-hold." It's also known as Catchbirdtree, for reasons I hate to think about.

The species is nearly "pantropical" -- native throughout the New World's tropics but introduced in many other places. In the US it reaches southern Texas and southern Florida.

from the March 13, 2011 Newsletter issued from Hacienda Chichen Resort beside Chichén Itzá Ruins, central Yucatán, MÉXICO
PULL-BACK-AND-HOLDS FRUITING
Pull-Back-and-Holds nowadays are laden with overlapping, spherical clusters of club-shaped fruits, as shown below:

The special thing about the fruits is that that they bristle with stalked, sticky glands. The fruits stick to you as with glue. A botanist writing on the Internet says that even on fifty-year-old herbarium specimens the fruits remain sticky. It's reported that birds can become entangled in the sticky fruit-orbs, though it's hard to imagine an adaptive advantage that might offer the plant.

While photographing the above fruits I began noticing a certain fuzziness about the bottoms of my feet. In what is surely the first picture in human history of the phenomenon of Pull-Back-and-Hold fruits sticking to the bottom of a human foot, you can see what I felt below: