Stewart McPherson was passing through LA so a group from the LACPS took him to dinner where he gave a brief presentation (on Nepenthes in the Philippines). He also donated to the LACPS library a copy of his latest book "Carnivorous Plants and Their Habitats" vol. 1&2. I borrowed vol.2 since it covers the glistening carnivores.
Regarding Drosophyllum lusitanicum he writes:
So much for gypsum, crushed coral, limestone etc."In Spain, Drosophyllum predominantly occurs in substrate that overlies quartzite sandstones and other sedimentary rocks types; all are very well drained yet chronically deficient in most essential minerals and nutrients. Contrary to most publications, Drosophylum does not grow in substrate overlying limestone (Jan Flisek, pers. comm.). In most cases, the substrate is purely derived from sand or sandstone and contains very little organic matter. Drosophyllum prefers acidic soils ranging from pH 4-5, but can also grow in strongly acidic to more or less neutral soils (pH 3.6-7.0;Adamec, 2009). Although the bedrock may sometimes consist of sandy limestone, the superficial layers of supporting soil contain little soluble calcium."