This section is from the book "The American Garden Vol. XI", by L. H. Bailey. Also available from Amazon: American Horticultural Society A to Z Encyclopedia of Garden Plants.
In 1633, Laet, in his descriptio indiarum occidentalim, lib. 18, says that in Venezuela there are trees which give out a liquid which coagulates like cheese, and which is eaten at meals. This tree, peculiar to Venezuela, was observed by Humboldt, who says that the vegetable milk of the palo de vaca [Galactodendron utile, H. B. et K.] has an agreeable taste and an aromatic smell. At Caucagua the natives call the tree arbol del leche, milk tree. The further account is quite pastoral. "On the barren flank of a rock grows a tree with coriacious and dry leaves. Its large woody roots can scarcely penetrate into the stone. For several months of the year not a single shower moistens its foliage. Its branches appear dead and dried; but when the trunk is pierced there flows from it a sweet and nourishing milk. It is at the rising of the sun that this vegetable fountain is most abundant. The negroes and natives are then seen hastening from all quarters, furnished with large bowls to receive the milk, which grows yellow and thickens at its surface.
Some empty their bowls under the tree itself; others carry the juice home to their children." Samples of this milk analyzed by Boussingault showed it to contain: - Water, 58.0; wax, etc., 35.2; sugar, etc., 2.8; casein, 1.7; alkaline earths, alkalis, phosphate 0.5 ; undetermined 1.8 per cent. Seeds were germinated at Kew Gardens, England, in 1881, and plants sent in 1882 to Australia, India, Feejee Islands, Java, Singapore and Ceylon.