The plants of the cerrado and caatinga ecological provinces of Brazil, the suggested original home of pineapple (3), have many and varied mechanisms whereby they have adapted to the frequent development of moisture stress. The pineapple plant presents a peculiarly interesting combination of those traits that have been proposed for xerophytic and sc!erophyllous plants (10, 15). Preferential collapse of the water storage tissue of the leaf in time of moisture stress is further evidence of the intriguing adaptation of the pineapple plant to water deficit (15, 19). Reduction in the daytime rate of vapor exchange from the pineapple leaf (14) could well be accomplished by the highly cutinized upper epidermis and the deeply entrenched stomatal pores with an overlying mat of trichomes on the undersurface. The very low rate of but 0.3 to 0.5 nig of water lost per cm2 of leaf surface in an hour contrasts sharply with the 26 mg from a corn leaf, and the 43 mg from a cocklebur leaf (23). Such restricted daytime gas exchange through the leaf requires some compensatory mechanism for a CO2 supply for photosynthesis. The acid metabolism of crassulacean plants has been shown to provide such a mechanism, and it has been reported specifically for pineapple (21, 22).