The actual number of poisonous plants likely to be inadvertently eaten by human beings is not large. Chesnut[14] has enumerated about thirty important poisonous plants occurring in the United States, and some of these are not known to be poisonous except for domestic animals.[15] Many of the cases of reported poisoning in man belong to the class of exceedingly rare accidents and are without much significance in the present discussion. Such are the use of the leaves of the American false hellebore (_Veratrum viride_) in mistake for those of the marsh-marigold[16], the use of the fruit pulp of the Kentucky coffee tree (_Gymnocladus dioica_) in mistake for that of the honey-locust[17], the accidental employment of daffodil bulbs for food, and the confusion by children of the young shoots of the broad-leaf laurel (_Kalmia latifolia_) with the wintergreen.[18] One of the most serious instances of poisoning of this sort is that from the use of the spindle-shaped roots of the deadly water hemlock (_Cicuta maculata_) allied to the more famous but no more deadly poison hemlock. These underground portions of the plant are sometimes exposed to view by washing out or freezing, and are mistaken by children for horseradish, artichokes, parsnips, and other edible roots. Poisoning with water hemlock undoubtedly occurs more frequently than shown by any record. Eight cases and two deaths from this cause are known to have occurred in one year in the state of New Jersey alone. [Illustration: FIG. 1.--_Conium maculatum._ The fresh juice of _Conium maculatum_ was used in the preparation of the famous hemlock potion which was employed by the Greeks in putting their criminals to death. (From _Applied and Economic Botany_, by courtesy of Professor Kraemer [after Holm].)] An instance of food poisoning to be included under this head is the outbreak in Hamburg and some thirty other German cities in 1911 due to the use of a poisonous vegetable fat in preparing a commercial butter substitute.[19] In the attempt to cheapen as far as possible the preparation of margarin various plant oils have been added by the manufacturers. In the Hamburg outbreak, in which over two hundred cases of illness occurred, poisoning was apparently due to substitution of so-called maratti-oil, derived from a tropical plant (_Hydrocarpus_). This fat is said to be identical with oil of cardamom, and its toxic character in the amounts used in the margarin was proved by animal experiment. Increasing economic pressure for cheap foods may lead to the recurrence of such accidents unless proper precautions are used in testing out new fats and other untried substances intended for use in the preparation of food substances.[20]