Research and photos thanks to Ken and Bea.
The Guamúchil tree produces a bean like pod which turns a little bit pink and starts to pop open.
The pods are produced by a tree member of the Bean Family, PITHECELLOBIUM DULCE. In English the main name for it appears to be Manila Tamarind, but that’s unfair, since it’s a native Mexican tree and was introduced into Manila, as it also was in many other tropical areas. In Hawaii it’s even become a weed tree. Around Jaltemba Bay the tree is called Guamúchil.
When the legumes mature they acquire a rosy blush on their exterior, split, and expose a white, pulpy material inside which black, shiny beans are embedded. You peel open the pods the way you would a big garden bean, eat the white stuff, and throw away the hard, black bean which is about the size of a watermelon seed. Some trees produce sweeter pulp than others. They are often for sale at the tianguis and from truck parked on the street but not common in local stores.
Botanically, the edible white pulp is the seed’s “aril,” which is an outgrowth from the funicle, which is the umbilical-cord-like thing connecting the seed to the pod’s midrib. In some seeds arils are bright and showy, helping attract potential, hungry seed-disseminators.
The “dulce” in the species’ Latin name led me to expect the white aril to be sweet, since that’s what “dulce” means. However, I found it about as bitter as it was sweet. In my opinion, this is another example of nature creating something that’s good-tasting enough to make you snack on it as you walk down a road, but not good enough to make a memorable meal.
Local Mexicans seem to relish them much more than I. The pods are even on sale in the market. I expect it’s one of those cultural things, like Limburger cheese or gefiltafish: You have to be born into the culture to really appreciate it.
Guamúchil’s leaves are easy to recognize. Above you can see how the compound leaves alternate upon the stem. Each leaf consists of two leaflets which in turn are divided into two asymmetrical leaflets, looking like butterfly wings. Therefore, each leaf consists of four leaflets.
The name “monkeypod” is more commonly used for the rain tree (Albizia saman). Other names include blackbead, sweet Inga, cuauhmochitl (Nahuatl), guamúchil … Description:
P. dulce is a tree that reaches a height of about 5 to 8 m (16 to 26 ft). Its trunk is spiny and its leaves are bipinnate. Each pinna has a single pair of ovate-oblong leaflets that are about 2 to 4 m (6.6 to 13 ft) long. The flowers are greenish-white, fragrant, sessile and reach about 12 cm (4.7 in) in length, though appear shorter due to coiling. The flowers produce a pod with an edible pulp. The seeds are black.
The seeds are dispersed via birds that feed on the sweet pod. It is drought resistant and can survive in dry lands from sea level to an elevation of 300 m (980 ft), making it suitable for cultivation as a street tree.