Excerpts from Jim Conrad's
from the August 31, 2007 Newsletter issued from Sierra Gorda Biosphere Reserve, QUERÉTARO, MÉXICO
A RED-FLOWERED GRAPEVINE, ALMOST
There's a full-fledged woody vine climbing into trees, securing itself with wiry tendrils tightly clinging to tree limbs. It's just like a northern grapevine, except that its leaves are divided into three leaflets, while you think of grapevine leaves as being a single broad blade. Also, this vine's flowers are red, and of course grapevine flowers aren't supposed to be red. You can see this handsome woody vine in full flower below:
From descriptions on the Internet, I figure this is CISSUS EROSA, apparently with no English name, growing throughout much of Mexico south through Central America to Peru. It's such a robust, pretty species that it deserves to be propagated horticulturally.
Belonging to the genus Cissus, it almost IS a red-flowered grapevine, since Cissus belongs to the Grapevine Family, the Vitaceae, and the genus Cissus is closely related to the Grapevine genus, Vitis.
The genera Cissus and Vitis are separated by the fact that Vitis's FIVE flower petals stick together to form a "cap" that falls off as a single unit, while Cissus's FOUR separate petals spread and fall off independently. Cissus fruits do look a lot like Vitis grapes, however. Most of them are pea-size or smaller, like the North's wild Frost Grapes, so they're great for birds but not so interesting to humans. The genus Cissus includes about 350 mostly-tropical species, while Vitis only has some 60 mostly-northern ones.