Cacao Culture in the Philippines
In the next step, every fourth tree in the fourth or fifth row of cacao may be omitted and its place filled by a permanent shade tree. The planting of shade trees or "madre de cacao" among the cacao has been observed from time immemorial in all countries where the crop is grown, and the primary purpose of the planting has been for shade alone. Observing that these trees were almost invariably of the pulse or legume family, the writer, in the year 1892, raised the question, in the Proceedings of the Southern California Horticultural Society, that the probable benefits derived were directly attributable to the abundant fertilizing microörganisms developed in the soil by these leguminous plants, rather than the mechanical protection they afforded from the sun's rays.
To Mr. O. F. Cook, of the United States Department of Agriculture, however, belongs the credit of publishing, in 1901,  a résumé of his inquiries into the subject of the shades used for both the coffee and