[Wikipedia] Seed Viability: In a famous long-term experiment, Dr. William James Beal, then a professor of botany at Michigan Agriculture College, selected seeds of 21 different plant species (including Verbascum blattaria) and placed seeds of each in 20 separate bottles filled with sand.[11] The bottles, left uncorked, were buried mouth down (so as not to allow moisture to reach the seeds) in a sandy knoll in 1879.[11] The purpose of this experiment was to determine how long the seeds could be buried dormant in the soil, and yet germinate in the future when planted.[11] In 2000, one of these bottles was dug up, and 23 seeds of V. blattaria were planted in favorable conditions, yielding a 50% germination rate.[11] (link added by Mary Ann Machi)