Saline extracts of the seeds of 262 varieties of plants belonging to 63 families were tested for hemagglutinating activity against human erythrocytes. Of these, 191 showed no hemagglutinating activity, and 46 showed non-specific agglutinating activity, and 46 showed non-specific agglutinating activity for all types of human cells tested. Extracts of the seeds of 25 varieties were more or less blood-group specific, and several in particular were specific for group A1 and A2 cells.
Extracts of leafy portions or fruiting bodies of 9 species showed activity in the case of only 1 species.
No specificity for the M, N, or Rh antigens was detected.
The theoretical implications and possibly practical application of these observations are discussed.