Abstract
SUMMARY: Nematodes and mildew‐infected barley leaves when examined in the scanning electron microscope after critical point drying (CPD) from sulphur dioxide (critical temperature 157–7°C) showed no obvious physical damage, but the specimens had a surface deposit which was probably heat damaged natural waxes. The nematode Caenorhabditis elegans and clover roots (Trifolium subterraneum) showed no physical or heat damage after CPD from monochlorodifluoromethane (Freon 22, critical temperature 96°C). The hyphæ and conidia of unfixed mildew on barley were damaged after CPD from Freon 22, probably due to the Freon extracting lipids from the cell walls. Freon 22 was preferred for most specimens as it is cheap, easy to get and not very toxic.