Prior to four years ago our patch testing of individuals in suspected cases of contact eczema from plants was a time consuming procedure. Because of the seasonal occurrence and the predilection of the eruption for the exposed areas, such as the face, neck, hands, forearms and legs, a tentative diagnosis of contact dermatitis of plant origin was usually readily made. As most of our patients came from rural communities and often from a considerable distance, patch testing to determine the offending agent was often necessary on the patient's initial visit. This required frequent excursions into the country to collect plants which the affected individual was most likely to encounter. Weeds common to the patient's particular locality often grew sparsely or only in certain parts of our territory. This frequently necessitated rather wide excursions for the collection of a few common specimens.
After the plants were collected the