1. The interactions between ragweed pollen and the saliva from ragweed-sensitive and non-sensitive humans have been examined. A number of morphological changes of the pollen grains take place under the conditions of the incubation. Of these changes, two occur only with incubation in allergic saliva and one occurs with the use of ‘inflammatory’ saliva, allergic or non-allergic.
2. The two changes that are associated only with incubation in saliva from an individual who is ragweed-sensitive appear to be related. They consist of a clearing of the background material surrounding the pollen grain and the formation of a halo of white, mat-like material around the grain.
3. The incubation of pollen with ‘congestive’ or ‘inflammatory’ saliva resulted in the exudation of granular material, encased in a membrane, from the pollen grain.
4. Kinetic studies give the development time of particular changes and their duration.