Discovery of the Function of the Pycnia of the Rust Fungi

Abstract

IN a letter to NATURE, published July 23, 1927, I showed, on the basis of experimental evidence, that Puccinia helianthi is heterothallic. The results of further experiments now enable me to state definitely that Puccinia graminis is also heterothallic. Moreover, since my first letter was written, proof has been obtained that the pycnia (spermogonia) of the Rust Fungi are not, as many botanists have supposed, male conceptacles producing non-functional spermatia, but are active organs having a non-male function which they carry out through the agency of flies. This discovery was made as follows.