Deppea splendens, coffee family, native to Chiapas, Mexico. The sign at the Conservatory said: "The last stand of these small trees grew on a mountainside in Mexico. Now it's thought to be extinct in the wild."
In 1981 a botanist collected seeds of this plant and distributed it to some west coast botanical gardens. In 1986 when he returned to the site, it had been cleared. The plants were gone.
The Huntington Garden in San Marino, California was one of the institutions that received the seed, and this plant is growing in the Conservatory there today. You can read about it at this link.
It is a tender plant, good in mild climates or protected over the winter in greenhouses. Plants grown from cuttings are available to purchase at the Huntington's annual plant sales, at several nurseries, or even through Ebay.
Sounds interesting, doesn't it? Wouldn't it be fun to help keep such a beautiful plant from extinction? If you're a gardener, you might give it a try.