Retrospective searching for poisonous plant vouchers.
Few published reports of plant poisoning, whether experimental or accidental, document vouchers. This can be rectified by retrospective location of vouchers through determination of a collaborating botanist or herbarium of deposit. An absolute voucher is referenced in the toxicology report. For a probable voucher the report does not identify an herbarium specimen, but the report and the specimen label or sheet agree on plant name, collector's name, collection date and place. A possible voucher is perhaps from the exposure lot, but was collected by the collaborating botanist at a somewhat earlier or later date than the exposure date. On the other hand, a supporting specimen was collected by the collaborating botanist but is not from the exposure lot. Vouchers and supporting specimens for some species of Asclepias tested for toxicity by CD Marsh and coworkers were found in the US National Herbarium at the Smithsonian Institution, Washington DC.