The best type of light tube is one which most closely resembles natural outdoor light: i.e. one that has at least 140 microwatts per 10 nanometer per lumen of blue spectra (440-495 nm). In contrast, warm-white fluorescent light has only 40-50 microwatts/nm/lum. and cool-white has 100-110 microwatts/nm/lum. Commercial lights meeting the photo-requirements of species mentioned in this book are the "Daylite 65" kind manufactured by the Durotest Corporation and having a "color Temperature" of 6500 ° K and the 'Vita-Lite" fluorescent at 5500 ° K. These color temperatures provide The proper amount of blue light for promoting primordia formation in Pleurotus ostreatus, Psilocybe cubensis and in other photosensitive species.